Is it possible to use the edding 5200 permanent spray clear lacquer to spray on hardened modelling clay (fimo air) to make the paint & figures last longer?
Yes, that should work. However, it is important to pay attention to the basis on which the colour used is based, so that no undesired reactions between colour and clear coat occur. But here it is best to test the compatibility in advance on a test piece or in an inconspicuous place.