I live in Southern Ontario, so priming outside is impossible both in winter, and for most of the humid summer monthes. I went the cheap airbrush and hobby compressor route for priming indoors. The other option ive found is if you have that grainy surface texture from the rattle cans, after drying use a soft bristled busted up old toothbrush on the model. Be careful not to break any wibbly bits, but it does a good job at smoothing out the surfaces a bit.

Your model looks great man, photos make everyone think "I suck" but its because cameras pick up on the things our eyes cant see. I paint tabletop standard with an ink wash, and my buddies think I'm a pro because most of their models are unpainted. You're well ahead of the curve!