Hi, I did mine last year and asked the advice of a good local mechanic. Basically you can do no damage here. If you don't have a power wash of your own you can take the car to the local garage and do it yourself for a quid or two. First remove the top plastic cover by removing the 4x 10mm bolts then you can either spray Jizer or another degreaser over everything that needs to be cleaned or use diesel oil and brush it on by hand. Leave it for about 5-10 minutes then blast it off with the jet wash, then hey presto you will have an engine that looks like new.