I’m trying to get more organized, but as of now my situation is similar to Matoro’s. I do have most of my minifigure parts sorted though, so there’s that.
The easiest way for me would be to look at the pieces and instantaneously build something using them. That way, I would have those pieces for access when I wanted to use them on a more substantial MOC.
I’ve been trying to sort my pieces by bagging up individual sets. I practically know what set every piece came from, so if I know that I need a lime-green foot, I can look for my Gresh bag etc.
I used do it all the time, but my entire G1 collection is in my parents basement for storage right now. I have bought a few HF and Chima ultra-builds since then, about five in total, so I have a few basic MOCs lying around. This is my brickshelf which has a little bit of my stuff, if your interested. I’ll try to get more uploaded there and post some stuff on the boards as well.