Oil priming question??

When should you prime the engine? Right before you start it?

Can you prime it a few days before you start it?

I was thinking if I could prime it early then I could get the distributor in, and bolt down the valve covers a few days early and everything ready before I start it.

When the distributor goes in, the number one piston has to be at top dead center?

Just to throw it out there off topic... Do you use gasket sealer on the valve covers? Or just the gasket?

Thanks!