I only buy generation 3 Montero but I figured this process is likely similar to many Mitz models.

I am in the process of purging / flushing all four of Montero coolant systems. I'm looking for the strongest and safest chemicals to do that with.

People online suggest the part store stuff is weak and bogus and I see people instead using dishwasher liquids/powders (like plain Cascade), white vinegar, or sometimes even degreasers like Simple Green, Purple Power, etc. Others use pipe/plumbing cleaners like TSP (trisodium phosphate) or CLR (calcium lime rust remover). There's at least a dozen other shelf ready or homemade concoctions.

What has treated you well and solved your coolant system problems?

My coolant systems in two of Mitz have just old/dirty fluids. Third one has oil in it from broken head gasket (about to repair that), and fourth may have a partially clogged heater core and old coolant.

I want to install a purge/flush kit to run water backwards through all their heater core lines. The yellow or blue plastic kits seem kinda weak to me but that's all I find available. Is there any custom hardware you've found works better and is stronger, and likely longer lasting? Maybe made of metal?

And I'm still considering what chemicals are best and potent for general cleaning as well as degreasing.

Any good or bad experiences?