75% overlap seems really unnecessary. I think i am generally at 10-20%.
Personally, i’m not opposed to going pretty strong on concrete pre/post. Whether that’s straight 12.5 xjetted, or like 50/50 direct… or even straight direct on something bad. That’s me.
Again, personally, i think a 18" will be pretty much ok with a 4GPM. I’ve never done a side by side comparison, though. I used a 19" with a 4 and didnt notice any issues, but that doesn’t mean that was the best way to do it.
You certainly dont need someone to move the hose for you while you are SC’ing, if that’s what you are doing – that’s a waste of labor IMO. Pull your hose before you start, and orient it so that it FOLLOWS you throughout the cleaning… like in a snake pattern or whatever.
No real reason to do the edges first, IMO. Dont know that stopping that will make a huge difference overall in time, since it all has to get done… but just pointing it out.
I also dont think you need to be stopping to rinse, unless stuff is drying particularly fast. Even then, it’s not super critical all the time, in my experience.
I would cut back on some of this stuff, and see if you have problems. If you dont, then you will save time by eliminating these extra steps.