Sounds like they are going on a bit heavy Dave. I have recently switched to Railmatch varnishes after various quality issues with Precision, I find it goes on superbly with a couple of lightish coats. Never had an issue with detailing getting too covered. Thats with quite a few coats too, 3 or 4 of primer, up to 4 for colour, couple of gloss varnish, then matt or satin, and finally weathering.
I think it was Tim Shackleton who once scraped an accumulation of spraypaint off a heavily used area of his worbench....after about 5 Years. It wasn't even a mm thick. Paint coats are measured in micron thicknesses, maybes try thinning your mix a bit more?