I have quite a lot of old paint in those tiny cheap tubes. the nice thing about acrylic paints are that they are water based.
I am going to try opening up the little metal tubes and dropping the contents into a little bottle then adding water and a little windex
The windex is a thinner (could use vinegar or a diff acid) and I have used it to good effect for my paint that goes through my airbrushes. If it works as I hope, I will drop the contents into little spray bottles for use.
Learned this trick when I worked for the Doll House Company
Updates to follow