This technique works for me:
I can seat GK SK's with a regular floor pump. When you get close to half of a bead seated using the tire lever, the half of the bead that's not seated is tight on the rim, so it holds air well enough pop in place.
My rims aren't hookless.
Another thought: if the rim has a matt surface, that might be impeding the initial air capture, so one layer of tape might fix that.