JW51 your rig up sounds very innovative and the items required though achievable but right now not something I would undertake.
As to Evaporust that KEVINSKI suggested or the vinegar mix could be a way out. And yes letting stuff like that evaporate and or dumping cat litter powder or powdered oil absorbing stuff seems like a way to dispose the residue.
Since the engines water pump and the block freeze plugs allow for partial access to the water jacket I’m tempted to soak those areas with Evaporust and or the vinegar solution to see what results I obtain. If the results are ok I’m thinking that while the engine block is on the engine stand I’ll cover up the large openings and pour the solution into the jacket. After that I’ll drain the liquid and let the solution evaporate and then discard the solids.
