Paint is very hard IMO
A pressure washer will not dent your paint IMO
The chemicals are very strong and I think they will remove some/most of the wax/sealant that you have on the car.
I would make up a kit that had everything that you would need to wash and QD and keep it in the trunk at all times.
I would also pick up the smallest vacuum you can find.
Lowes/HD have very small one's for under $30 on sale.
Offer to wash/QD/vacuum other people's car in exchange for the use of their water/electric.
A $50 DOLLAR VALUE
Most peole do not even give washing their cars a second thought and what ever you do will be a big upgrade for them.
Find somthing to spray/apply to the inside of the car to make it smell better/nice and wipe dowm the dash pad anythigh else you can