yes I understood what you meant by oil every where, like I said, when a hose blows, it can get every where FAST, there is a ton of pressure in them hoses and when one gets a hole or leak, things happen fast and large amounts of fluid can get out and on things fast, pending HOW fast the operator is ir isn't!
and keep in mind, many hydraulic systems use 10W30 oil and not just hydraulic fluids, and all fluids can get dark as time goes by, and many owners of equipment are not always the best at changing fluids often,
so having DARK oil every where again is not uncommon!
cleaning belly pans out on machines is also an over looked condition by many owners
there even know to cause fares from debris in them building up and catching fire due to lack of being cleaned out often!
add in oil from either fill spills, or leaks or changing hoses, and its not hard to have a very oily machine for many operator's/owners, that don't want to spend the time to clean things, we all get lazy some times, but some are just worse than others,
and why many times its so hard to find a good cared for older machine , when folks are looking to buy one
seems almost like more bad owners these days than ever on lacking maintenance on things, as so many have disposable mind sets, !
any how, as for recommending a good de greaser, honestly there are tons of good one's on the market these days, , it might be easier to ask your local HD equipment shop what they use and sell, making it easy for you to acquire from them! as pretty much any good shop will have one brand they use and like and most will sell it as well!
but a simple search online will provide you a long list of good ones
like this off amazon, sure it can be had other places too, and should also have a bunch of like products on same link to view and pick from!