Power washer

They are the quick way to get water ingress in leisure vehicles unless much care is taken and they can strip vinyles  in seconds

Used with care, they are fabulous labour saving devices and can be used on roofs. I use a Karcher.

 When I had the "Autocruise" I did the roof first with a patio cleaner and a broom,then rinsed with a bucket of water and broom.Preasure washers in general are bad news for our vehicles as said . 

Just don't. Not worth the risk in my book.

You may have the message power washers are not good ! However I use one purely to drive a snow foamer, not for rinsing down. You will find a light wipe with a sponge removes dirt better than a power washer on a polished surface.

I use Fenwick products for mhomes, as the cleaner is formulated for materials used on them. Not many cars have vinyl decals, acrylic Windows and loads of sealant and maybe specialist body panel materials.

I have a 8 metre long , 3 metre high mhome, so takes a bit of cleaning.

i work a side at a time, starting with the roof. Luckily I have a tall step ladde that I can use a long washing brush to reach over the roof area.

i snow foam using Fenwick cleaner, let it sit for five minutes, then scrub off. Rinse off, then use Fenwick Bobby Dazzler as a final rinse, Then I repeat on each side. A wipe down after using Bobby Dazzler, with a micro cloth leaves a decent finish (until the next road trip ,)

Depending on the manufacture recommendations , a silicone free polish and wax may be required to finish off. (Marine chandlers are best source for these items)

Rgds

I use step ladders. Have to careful they don't bang into the side of the van [some people pad the ladder edge]. Usual health & safety concerns apply for working at height! Then I use a long reach brush from all four sides. This means some parts get cleaned twice. I have a short handled soft brush for going around roof lights, the TV aerial and guttering.

My choice of cleaner is BioPro's CaraPac wash n wax. Sometimes I additionally wax the roof with Autoglym using the long handles pole with microfibre cloths covering the brush end. There are numerous products available and all make claims which may or may not be true. CaraPac works for me and BioPro say the product is environmentally friendly. Not easy to get hold of though.

You wouldn't give a chainsaw to six year old (nor should you use one yourself without proper training and protective equipment) but used correctly they are immensely useful. 

Likewise a power washer is very useful for cleaning your M/H and I do use one.

However the potential to remove mastic seals decals or even paint is real if you use high pressure especially if the nozzle is close. You pressure wash kit should have come with a variable pressure lance (if it didn't you can probably buy one as an accessory) and if you set this to a gentle pressure it is very useful for washing down.

I mainly use my jet-wash to cleaning mud off wheel arches and mud-flaps (medium pressure  used carefully). Additionally with a professional snow foam dispenser the pressure is very low and speed of application fast as the vehicle is foamed using a wide arc. After leaving for a few minutes the foam is removed using the lowest pressure setting. Very simple and very effective and something you can do in winter when you wouldn't spend hours doing a bucket and sponge job. 

I never use commercial jet-washing (coin-op or manual operator) because you have no control over the pressure settings on the equipment. 

So in my view jet-washes have their place but must be used with care and respect.