preparing oil seals

clean out the mating surface of the metal and apply some oil or grease to the inner diameter where the shaft goes.
 
Any engine rebuild that I've done you just make sure the seals are wet with a lube that it seals against. Automatic trans u can use vasoline as a lube on seals and hold the check balls in place till you put all back together, and it won't hurt the seals or cause problems with the lube it seals in since it's petroleum based. Not sure about 2 stroke app thou.
 
Greases the seal lips or they will burn up on the rotating shafts, I see wheel bearing seals all the time that I have to peel the lip off of the spindles because they were installed dry!