I think TFRs are generally OK as long as you don't leave them to sit for many minutes. It's reallly a spray it on and rinse it straight off type of product. As pointed out they are pretty potent chemicals.
I normally use Valet Pro Citrus Pre Wash diluted about 6:1 as a first step, leave it to dwell for about 5-10 minutes then pressure wash it off. I find this cuts through the worst of the surface muck effectively, especially the salt spray at this time of year. As a second stage I then use Magifoam and leave this to dwell for 30-40 minutes while I clean the wheels before rinsing and washing the car.
I normally use Valet Pro Citrus Pre Wash diluted about 6:1 as a first step, leave it to dwell for about 5-10 minutes then pressure wash it off. I find this cuts through the worst of the surface muck effectively, especially the salt spray at this time of year. As a second stage I then use Magifoam and leave this to dwell for 30-40 minutes while I clean the wheels before rinsing and washing the car.