I use it full strength in a gardern sprayer to soak stuff down then use a good strong water hose
to rinse. or one of the cheapie pressure cleaners with the 1,000 psi works pretty good from HF Tools.
I have a really good $700 pressure washer.† Would you recommend against using that because the pressure is so high?† I could put on the widest tip I have.
Use the wide tip and soak the area good with Purple Power for about an hour. Sometimes it helps to spray water on some of the areas before application but only if you think it needs a little extra moisture.
Spray it down at 4 to 6 inches away to get the first layers off, Let it drain and coat with PP again and let that soak for about 1/2 hour.
Then power wash maybe a little closer as needed. If you don't get it all the first couple of tries. Spay PP on the worst areas and let it sit
overnight then wash it down again.
I have used this process many times on Transit buses that were so grimed up that you couldn't tell there was an engine in there...
Most looked like new after a couple of treatments, Clean enough to repaint. One had 1 1/2 Inches of gunk on the bulkheads
and one good twice-over and then a low power pressure washer took it all off.
Just make sure to wrap sensitive stuff in plastic or seal with duct tape around connectors and switches before the cleaning.
Oh... Be sure to do the cleaning somewhere that the 50 pounds of dirt, crap and residue won't be a big cleanup problem.
Whatever you do, Don't use Oil-Dry or Cat Litter to soak up anything that has water in it. The Bentonite Clay turns into a gummy
mess of slick-slippery and messy Owl-SNOT... Impossible to clean up or even wash away..... Don't ask how I know that !!!