We've got a real problem with one product where we use potting compound to encapsulate a PCB assembly.  The PCB has a few relay sockets which have some openings at the bottom of the socket - not sealed.  When we pour our potting compound into the unit, the potting creeps up the connection pins into the connector body itself which really fouls up our ability to plug in the relay. 
 
Getting the sockets sealed at the factory is not easy - big minimum order and very costly.  We've tried a two stage potting procedure where we pot only part way until the potting reaches the level of the socket - then let it set, then pot the rest of the way.  This works to some degree but with mixed results.  
 
We were thinking of sealing the bottom openings with a peelable solder mask (Alpha Solder Stop 110) but some here were conerned that this could adversly effect the tin plated brass pins on the socket or the solder joints themselves.
 
Has anyone else ever run into a similar problem?  Anyone think of anything to try in order to help this situation?