Free weed update:
I have the empty solo cup in the new pot to make sure the soil is about the right level. I watered about a pint in each 2 gallon pot, about half right around the cup, then let it soak in a few minutes.
When I pull the cup, I have a spray bottle ready to soak the soil inside if any is dry and to help hold the soil together and keep the hole from filling in, then I dust some Rhize-Up in the hole.
With the split cup, I water it the night before transplant then let it drain for a while (overnight) and it helps the soul stick together without waiting for it to get more rootbound.
I open it halfway then close it, roll it, then open the other side up just to make sure it doesn't stick - then replace your hand for the other side of the cup and roll it out. No turning it upside down, all the roots should just keep going, none torn or damaged, etc.