In Karachi there were some industrial degreasers available, which were supposed to be used after dilution with water - they worked really great. Similarly in the US I use simple green aviation cleaner, recently I worked on the front of my cars engine - in a 6 cyl W124 MB there is about 2 inches of workroom - and I had to remove the radiator, fan etc too.
A little petrol mixed with ATF, a toothbrush and 1 hour of time, really softened or removed all the old black oil grease that had accumulated since 1995. Another washoff with simple green aviation cleaner and a clean brush did the rest - followed by a spray of WD40 to protect from corrossion on the bolt heads and timing case.
In Pakistan I used the citrus industrial cleaner - diluted to about 1:10 ratio. For real heavy grease/oil petrol+ATF+brush+patience. If you have old burnt hydraulic oil residue or burnt grease residue then a can of brake cleaner is your saviour. That stuff is NASTY and will remove all sorts of petroleum oil.
Please always use gloves when doing such stuff, your hands are very expensive to repair and these chemicals can also get into your skin - which is bad.
If you have back problems then its best to raise the car to working level so you dont bend that much and wear a back brace to assist you.
