I worry about getting degreaser in the jockey wheels and the bb.
how do people clean there rear mechs?
for chainrings and cassette on bike cleaning I use neat degreaser and a wee brush – I find the aerosol ones tend to go places you dont want, like jockey wheel bearings BB etc, whereas a small brush, some agitation and a rinse does the job. Remember to put a drop of chain lube onto the jockey wheel bearings at the end – keeps them running quiet and smooth.
I think the big difference between how the pro guys do it and how we ‘should’ is that they are driven by short term performance and appearance, where we are driven (or at least i am) by both performance and longevity of components, hence whey it is easy to question their use of jetwashes and airlines