This sounds daft, but having dedicated clothes to do dirty work really does help. I’ve only recently realised this. I bought work trousers, shorts and waterproofs from B&Q which were cheap as chips and much better than old normal jeans, because they are much tougher and are cut much looser so they don’t restrict when you are crawling around under cars etc. Also I wear gloves wherever possible to keep my hands clean of toxic oily grimy crap.
However, for the bike I just wear an apron (some eBay one not a Park one, I’m not a poseur 😉 ) which is brilliant as long as I’m in short sleeves.