I don't use degreaser; I don't want emulsifiers near my bikes. Anything that lets oily substances mix with water is bad, I reckon. That includes WD40.

If I acquire a used part that's caked in grease, I clean it with solvent and a rag. Otherwise, it just doesn't come up, because I wipe excess lube from my chain, and I don't have excess lube anywhere else either.

My bikes get dirt on them, which comes off with a damp rag.