I use TFR with wax just pre spray it then give it a quick brush then power wash it off job done takes me about 30 mins to do but the double unit takes about 1 hour.
£30.00 for the 1st caravan
£85.00 for the double
You dont need to use a power washer but thats all ive got, a hose pipe or WFP will be just as good but you might have to brush a little harder to get all the green out first before rinsing.
Be carefull to dilute the TFR i use 1 part TFR then 5 parts Water.
If you need any more help let me know...
Cheers
Bazz...