PS. There is absolutely no reason to have oiled burned all over your engine. At least it's never been a problem for me. I make cleaning the engine and the engine compartment a regular part of cleaning the plane. I've seen planes that look like they've planted sod in there.

If you have an air compressor, use it to blow dirt from the engine and also blow crud from places that are hard to clean such as clevises, hinge lines, wheels, etc. Does a great job. If you don't have a compressor, then squirt a lot of water or windex in those areas to float out the crud.