Tokyo Marui pistol builds

I've been interested in the Airsoft community for a long time. The Earliest guns I've owned were spring based. Remember I had a Scorpion with a foldable stock. Earlier this year I really wanted to get my hands on one that runs on gas. I'm interested in modifying whatever I'm interested in so I was pointed in the direction of Tokyo Marui's 5.1 or 4.3. So I got a 4.3 and I love it! I also enjoy target practice so that's what I was doing during the summer. I bet over 2k rounds got out. The only aftermarket parts I've bought would be the

Slide (La Brama, which I detest because of the flaming ball),
ProHandgun Steel outer barrel (for compensators)
Compensator to match the slide,
Trigger and bow (probably ILLusion Kinetics),
150% hammer & guide rod spring, (9ball)
heavy duty loading nozzle (9ball)
PDI tight bore barrel
Mini red dot from Swiss Arms
CQB Light from Swiss Arms

Then later I proceeded to get frustrated and wanted to do something so I started to sand down the paint off the frame and most parts. It's not done yet. What do you guys recommend to sand with? I mean, to get it all polished?

Trimmed the dust cover also.