I did mine by myself as well. I did put the ends on first, then carefully lifted with legs & slipped in the first bolt on one side, then another on the other side. With the weight of the bar on them it didn't slide off, so then I could spin on the nuts & then get the rest of the bolts in & tightened.
I didn't want to be underneath trying to bolt on the ends... As it was I mashed a finger tip & split the nail half way up when the socket slipped off... I think I said, ummm... "ouch."