I hear you, I've never liked rattle cans, but I foam-smith.
Although I've been painting my costumes for over 10 years by hand, I recently switched to airbrushing! I would recommend a cheap airbrush if you can afford one. It makes the painting application far easier and smoother with a nice finish. I use watered down latex house paint or cheap acrylic paint, and it works wonderfully. I can also airbrush fully inside when using non-toxic paint.
I use a cheap 60$ brush with a second-hand air compressor I bought for $70, both the Iwata brand. Totally worth it!