When installing a new converter, I supose it would be a good thing to fill the converter as much as will stay in it before stabbing it onto the trans.
If its already in the car, then there's not much you can do there.
Yes it does take a couple seconds for the pump to flow, but thats about all it takes. I think most pumps flow about one quart per 10-15 sec at idle. So you have just over a minute before the 4 quarts in the pan is emptied.
When I re-build a trans, and I think most builders also, the pump is pre-primed or lubed and all internal parts are prelubed. Also the clutches should not experience any hardship as the there is enough clearances in the clutch packs to allow them to spin rather freely. Hammer down should not experience any new trans/dry startup issues as his unit is already prelubed.
Since HammerDown indicated that he drained the converter with a previously installed plug I assumed it was empty, and that the trans was still installed in the car.
Kudos to you HammerDown on doing that full trans service. Most folks never even think about the tranny untill it starts to act up.