The most fun was anytime I raced. Fun cars like my Royale Formula Ford, several Formula Vees, a couple of Miatas and the most fun was the '60 Bugeye Sprite. Fun tracks like VIR, Road Atlanta, Roebling Road, Barber Motorsports Park and Taladega Grand Prix Raceway.
Can you give us an idea of your mixing ratios? I've been mixing 100 ml batches of acrylic thinner and add 2 ml of Liquitex Professional Flow-Aid Fluid Medium and 2 ml of Liquitex Professional Slow Dri Blending Medium. I usually thin the acrylic paint 1:1 with the thinner mixture.
220 is too coarse. You need to finish sanding with something finer. I usually go with 360 or 400 to start, then 600 to 800 and finish with 1000 or 1500. The smoother it is before you spray, the smoother it'll be after you spray.