Under normal operation, how much oil should I be seeing arriving at the top of the rocker assembly?

This is a fresh B20 rebuild with essentially all new components. Oil pump was primed with a drill and hacked-up jumbo flat screwdriver. Took longer than I expected to get oil to the top of rocker assembly, and I'd describe it as more of a drip from the holes rather than a "squirt". Started it up and ran for 20 minutes from 2000-3000 RPM, with no unusual sounds or smells. No idiot light on dash. Peaking into the oil filler hole, everything appeared wet. Have not started it since. It was pretty cold out (for GA, mid 30's), and I had 15W40 Rotella in the pan, so viscosity may have been an issue.

I've ordered a 0-100 psi VDO oil pressure gauge and sender, but in the meantime I'd like to try and visually confirm I'm getting a normal amount of oil to the top end. At idle or a fast idle, should I be able to leave the valve cover off without making a huge mess? Should I be expecting "bubbling crude" or a "gusher" (have not actually tried this yet). I've got a lot of time and money wrapped up in this project and I'd sleep a lot better at night knowing what I should be expecting.