And even when i think i have succeeded my balls come back out when i try to pull my homemade gaff (i think the sock part was too small)
Lots of it is just practice. I never tried a gaff, I just use my panties. Every once in a while one will slip out, but usually if I have those things up in their holes, and my clit pulled back tight enough (between the glutes usually works for me) everything stays in place.
This. If you're having issues, try keeping your scrotum stretched after tucking them up there. As long as it is, they physically can't come back down.
I should mention, also, with practice, nothing is actually *needed* to hold things in place, at least for short periods. For example, I will often tuck right after drying off from showering, and shave before getting dressed.