IMEx Hair spray will yellow with age. It has a bad effect on some materials and can remain sticky when either humid of hot, This attracts dust as it sort of rises to the surface.
Really the only way I have found is good long term is to use woodworking PVAs under and or varnish as a very thinned spray top coat.
A Question guys, is the woodland spray gule just PVA thinned ?? sure looks like it
AJ.