You don't have to wait until you get the leveler. Druss is correct that ideally you shouldn't be using the swash plate to correct other problems and the closer you get it to perfect the better it will fly (though nothing is ever absolutely perfect and a little trim isn't going to hurt). But if you have a good eye, eyeballing it is good enough to get you in the air. You can always adjust it again later with the leveler if you really want. I've been able to get it very close by eyeballing, with little to no trim adjustment needed at all when the heli is balanced.

Heck, you don't even need the swash plate leveler. It's a convenient tool, but anything that you can fit in there that has a right angle (like a small t-square as Druss said or anything rigid and square) will work.