Have you considered sitting them "in" a water source??? You know, Heavy watering and a saucer to hold extra water while you're gone??? Their feet would be wet for longer than normal but something to consider...g/l
Make sure to fill your pots almost to the top with dirt...you may have 5 gallon pots but they're only 2/3 full of dirt...you're really only working with a 3.5 gallon pot currently...g/l
Personally I don't use strings or ties...I make different length "bo peep" hooks out of metal wire hangers...it makes it easy to move or remove as she's growing...g/l
If I know going into a grow that I'm going to use LST, I don't put the plant in the center of the pot during the last transplant...ill offset it drastically towards one side of the pot and that gives me an opportunity to bend and train the plant sooner to go around the circumference of the...
There are many ways to transplant no doubt
When I transplant 1. If the soil is moist I pack the soil down into the pot before I invert it...and B. (haha) if the soil is dry I water it, pack it, invert it and then transplant...and also, plan your transplant in advance...give it a try.g/l