Glyptol is commonly used to coat the insides and windings of electric motors. It is that red colored paint you see when you look inside one.
Check with a local electric motor shop or perhaps even W.W. Grainger. Alternately, engine builders used Rustoleum back in the good old days to promote faster oil drain back through the block valley and upper cyl head areas. With either paint cleanliness is an absolute must before applying.
