This is a picture of the probable floats I will be getting. Lots of sizes and shapes hopefully to make them for many different fishing needs.

Any suggestions for a paint to use that will stick the best on the plastic if I can not remove it? Also, what would be the best way to secure the bb's in the tube so they don't move too far up the tube if I need to do so?

I am also kinda stuck on how long I should make the shaft out the bottom. I see lots of floats for lots of species that have a really long metal rod out the bottom supposedly for stability. Is it needed to stabilize a float in flowing fast water or is it really needed if weight properly?

I wonder if it is possible to powder coat plastic???? Assuming the melting point is well above 500F of course.