I've had success with Tamiya clear coat by spraying a few light dusting coats on the decals and body then following up with several medium coats. The light dusting coats will cover the decals but won't degrade them (I use Detail Master decal paper that has been printed in a laser copier).
I even used this method to spray directly on the decal sheets to protect the printing, which works pretty well.
YMMV
Greenman62
I even used this method to spray directly on the decal sheets to protect the printing, which works pretty well.
YMMV
Greenman62