I take mine completely apart (including removing the O-rings)and check to make sure there is no loose metal chips, etc from machining. Then I port them like a cylinder head and remove any sharp edges the oil may have to pass over. I also check the pressure relief valve for proper fit and any machining irregularities to make sure it won't possibly hang up once assembled. I also check all mating surfaces for flatness and proper clearance for the gerotor pieces. Once I am sure all is good,I clean it up with brake clean. Then I lube up the inside with some Vaseline and put it all back together lubing all O-rings. Before I mount it to the block, I coat both sides of the paper gasket in a light coat of gasket shellac and then assemble right away. A little putzy, but it's the little things that will get you.
100%
NEVER EVER just bolt an oil pump onto an engine without complete blue print of the unit. Remember that this is probably the single most important component of your engine.
I use a small Dremel to de-burr and smooth out the passages then wash and rinse with hot soapy water. Then Vaseline or assembly lube everything.
Gus