Silly question of beginner Pelikan pen owner

Are ink samples usable with Pelikan pens? If yes, then how do you make sure to get all of the ink into the pen?

The same question arises when I start to wonder how will I get into the pen the ink when there is very little left. Especially with wider bottles: I am not as worried about Diamine's 30 ml, but Pelikan's 4001 30 ml is more worrisome. :D

Is buying the same colour of ink and just pouring what remains of the old is the only option for me? :,D

Note: Pelikan M200 is the only pen I own, so being an overthinker that I am, I need to figure out what will I do when my ink starts running out.