I have a Demon Hurricane P4 (3000psi 15lpm) and use a demon FSC most of the time (also a whirlaway) I use the Demon first as it does not spread crap every where, then a quick rinse with fan lance, do the edges with a turbo, any areas that need a bit more I use turbo again then rinse,
I make sure the FSC is set to the right height (quite low) dont have any probs doing it this way