Just so you understand where I'm coming from, I'm a professional frame painter (and builder and teacher too of course) that insists on doing top notch work. I don't pay too much attention nor am I critical of hobby methods of painting. They find solutions to inexpensive and home made methods of getting the job done. I have all the right equipment and paint and painting aids to do the job the best way possible. And just for the record, I have been painting for 45 years and done thousands of jobs. I can never afford to put out a job that is less than the equal of any other really good painter. The 35 years is how long I've been using House of Kolor paint. There was a bit of a learning curve using that paint instead of Imron (I still use Imron sometimes). I've also taught a few other pro frame builders how to paint as well. I figure on average it costs me about $150 for just the paint for every frame. That is not including overhead.

As I understand it, using good paint mixed in spray cans at auto paint stores works well although I've never tried it. I recommend putting a couple of coats of intermediate clear very soon after putting on your color coats. I'd let that harden very well and then wet sand it with 600 grit. Now you have a hardened surface to put on masking tape of any kind to orient your decals. As you've noted, you only have one shot to do it right. I always mark the masking tape so there is no mistake on where to place the decals. Then I apply the final clears. I doubt you have the resources to do this but the show quality way to clear decals, is to put multiple clear coats with sanding in-between so that the final thinned out clears leave no bumps on the decal edges. If your final clears do not have that high wet look gloss, there are ways to polish it out until it does. That process is for another post another time.