When I do all my planters for the summer, I usually do them in the garage where I have a decent padded folding chair, so I can sit in the shade and plant them all and without bending over. I can also make a mess there, the smooth concrete floor is much easier to sweep up than the patio concrete.
To move them in place, I have a flat dolly (basically it's a rectangular frame with wheels that I put a 1/4" board on it) that holds multiple planters and I can just pull it where it needs to go with a cheap attached chain or rope. If you have a planter too heavy to move, just move the chair to the planter, I make sure the area is in shade if I have to do that.
I have one of those benches that you can sit on when doing pruning or weeding for long periods of time instead of standing and bending in the hot sun. They usually have pockets to hold your tools as well.
One thing that requires a lot of time and bending, when I have to remove a lot of grass to make flowers beds or widen them, I just sit on the grass and do it. It goes so much quicker and so much easier. When I first decided to plant perennials and had to pull up grass I thought it was going to take me years for about a 65' x 3' wide length whenever I tried to tackle it. Then I tried just sitting on the grass and doing it and I got it all done in 2.5 easy days with a tool that just cuts through grass and roots.
