Any primer will work, just depends on which one you like.
I use Duplicolor most of the time.
Here is some videos i did on them
http://www.youtube.com/watch?v=b5A_m9NSrdc
http://www.youtube.com/watch?v=ZH7rRu2cagc
As for sealers it depends also.
I use testors Dull Cote to seal all my skins.
http://www.youtube.com/watch?v=BlEtoT4MvFQ
But if i want glossy look i use Pledge floor polish, can get it at most super markets in the cleaning sections.
Testors also has a gloss cote as well, good stuff.
Garage Kit Colors has a bunch of sealers and primers as well to push thru a airbrush. I love their flat cote, it can dull shiny paints amazing and well worth it.