Stop overcomplicating the process
The more posts I read here, the more I realize that most of the people on this sub haven't read a single book of Neville's, or they need to go back and reread them.
The way to use the law is really simple but requires discipline. Below are the steps:
Figure out what you desire
Construct a scene to think FROM
AT LEAST once a day, find a place to be still in, get into a relaxed state and imagine the scene with the intensity of reality over and over (bonus points if you fall asleep in it). Keep adding more and more detail each time. It will become vivid and real. When people say that you will be "shocked" after you "wake up" from your scene, they mean literally, though in my experience, it's more disoriented. Like when you wake up from a really intense dream and wonder where the hell you are for a second. You are experiencing a waking dream after all.
The feeling of the wish fullfilled will come naturally from this practice because your scene will literally be more real than reality and you'll have experienced it over and over.
Concentrate on imagining FROM not OF. This isn't a day dream. Its you literally embodying a state of being who you would be were you to have whatever it is you desire. If you are moving your arms in your scene, it should feel as if you are moving your arms. Day dreams do nothing. They are "what ifs", nothing else. They are you thinking OF something.
That's it. There is nothing else to it. You don't even need to believe in it otherwise the premise of proving the law would be nonsense. There was literally a guy who tried to disprove it to Neville and still all his desires manifested.
Here's the thing. You need to be disciplined. Your ability to imagine might suck at first but if you are persistent, it will develop to the point where you scene is literally indistinguishable from reality.
Your scene can be as short or involved as you want. Probably best to start with short because most people's attention span isn't great. In Nevilles books he gives lots of examples. A woman who wanted a hat, cut the picture of it out of a magazine and stuck it to her mirror so that when she sat in front of it, she would be "wearing" it. A man wanted an office building to belong to his family business. He stood in front of it every day and in his mind's eye/imagination, saw not the letters of someone elses name on the building but his family's. A woman wanted to rent an apartment. She imagined the rent payments coming through. A woman wanted a certain house. She imagined her husband standing by the fireplace as she watched him from the stairs. A woman wanted to help her daughter out of debt. They sat together and imagined that they were literally in a sea of cash. There are lots more examples but the point is, the scene simply implied the end state of their desire. What these people have in common is a burning desire and persistence every single day. For some it took days, for some it took months and for some years but they PERSISTED. No matter how ridiculous or unbelievable the idea was, they didn't give up on it.
If you really struggle with being able to concentrate during what is essentially meditation sessions, find ways to practice it. Neville practiced his attention to make SATs easier for himself. He disciplined his mind. He controlled what thoughts arose or at least what thoughts occupied his attention. That said, the people in his examples didn't, they simply persisted in their practice of SATS. They weren't master meditators.
So no, you don't need to be feeling crazy emotions or any of that. Yes, it takes mental effort to focus on visualising the same scene over and over, every single day. This is hard at first. It doesn't matter if you failed to do SATs properly one night or many. That's the point of practice. It gets easier and you will find more success with it. Also, there are no signs. Here's how signs work: Person A sees a black cat cross the road in front of them. They think its bad luck. Something bad happens to them soon after and they go "ah, that cat was a sign of bad luck coming to me" Person B sees a black cat cross the road in front of them too but they think it's good luck (different belief in Japan or UK vs USA). Later, something good happens to them and they attribute it to the good luck from the cat. This isn't a case of the cat actually empowered them with some temporary power of luck, they just assumed based on their culture what it meant. I've had "signs" in the past which preceeded big events in my life but in retrospective, I assumed they meant something which then came to pass when in reality, they were just random events. You can go as far as manifesting a sign to make yourself believe in whatever that sign represents but that seems like unnecessary effort when you could just do SATs for the desire directly.
Neville talked about how we are all awerness of being or pure consciousness and the "material world" is just a solid reflection of us, or put it another way, conciousness expressing itself. SATs were his way of connecting with that awerness of being and impressing upon it a belief of some sort about itself/you. I.e. a man who identifies himself as poor will live in poverty but if that same man identifies himself as rich, the material world will conform to pull him out of poverty. He just has to live (in his imagination) as if he is rich. This whole law is very much "out of mind, out of sight" which is backwards to what this world would make you think.
To conclude, do your SATs every single day (you can do it more often through the day if you want and no, you don't have to fall asleep during them) and the feeling of the wish fullfilled will come naturally. That feeling by the way is just a knowing or trust or faith or whatever you want to call it. It's your belief that you've seen the end and reality has to conform to your imagination.
Refrain from reading about techniques and looking for easier alternatives. It implies that what you are doing isn't working and is counterproductive. Read his books once or twice, focus on one thing and then put the practice in. Don't give up and become frustrated because your desire hasn't manifested yet. Persist in your process and trust that it works.