I'm getting my feet wet with spraying in preparation for a bunch of small projects for Christmas presents. I have a big 2-stage compressor, so I decided to go with a cheap HVLP conversion gun to start. I got the one from Harbor Freight that seems to have good reviews there and on Amazon. It seems to be working well except I'm getting leaks where the cup screws onto the top of the gun. Should there be any type of sealant or gasket on that connection?