Fixing the scratch:
I waited six months and was finally going to varnish this and take it in for hi-res image to enter it into a competition. Had a brand new fine brush and was dusting it and slipped. That's an 11cm/4.5" scratch. It's not deep - I can't feel a gouge. Apart from mixing up all those subtle colour shifts does anyone have other tips on fixing it? This is just a very small section of largish painting.
Cleaning: I was cleaning it with cotton buds and a little saliva. I noticed paint on the cotton bud which implies pigment not bound. Is that normal? Does it need oiling out?
Varnish: I may one day shift to spray varnish but currently have bottle of gamvar to finish. I need to do it in dusty shed and seriously, don't want it impregnated with dust. I decided to clean section of workbench and create a tent using a new painting dropsheet. Any better ideas?