What tires are you using? I have a set of wheels with Rhyno Lite rims and have found it to be a challenge to mount new Kevlar bead tires. I almost never have to use my VAR tire jack but did this time. The tires seem easier to mount now that they're stretched a bit. Follow the excellent advice posted by others above, stay patient, and you'll do fine. Building up your thumb muscles is always useful.