hi tiggi a guide coat is a light coat of a contrasting colour to your primer usualy black is used over light coloured primers
what happens is "as you will tell from the images" the sanding is made easier and all the faults in you prep are shown as the black will remain on any unsanded areas or in any pit holes ,these pit holes can be filled with stopper then sanded flat
this is why i always refer to sanding as flatting the idea being to atain a perfectly flat faultless surface to paint onto
this also has the benefit of showing you when the sanding is complete thus avoiding breaking through and having to reprime
its common practice in the automotive refinishing trade
the crayons are Lydia,s my four year old daughter as she doese a bit of artwork as well
paul
