Blimy all gets a bit complicated ,as a life long chancer and bodger of kits my short cut failures have led to me to a couple of hard and fasts , I (thats me not you)can put any type of varnish over any type of finish it depends what you put over the varnish ,dont throw thinners type products at enamel varnish acrylic stuffs ok ,acrylic varnish will take all the abuse thinners/enamel type products can put its way.
I can under stand with the jumbo scale wingy things the chaps need a perfectly smooth surface with roundels as big as a ten pence I often think more skill needed to apply than what has been used to build the kit ,but from a chancers view (thats still me not you) all that varnish coat just for a couple of
decals if you've put down a decent coat of paint with the
airbrush it should be smooth anyway whats wrong with a dab of decal setter.
I've only just I must admit in a vain attempt to improve my modelling started to use varnish ,once model has been airbrushed to my satisfaction its given a satin coat(acrylic) left to harden then
decals applied put down with some decal setter then softener on top and thats it dont seal them in nothing just start washes and weathering even the finished product gets nothing as they are the tones and colours ive worked towards and dont want to alter them with yet another coat of varnish .
For thoes of you with varnish o phobia I to suffered but no longer go on YouTube look for VMS Varnish what the bloke does is horrifying proper behind the sette stuff but I can only say this product is outstanding and fool proof grab some from John at the SMSHOP you'll never look back.
Dave.