I use the AutoInt/ValuGard version of the acidic decontamination stuff. Works great for me. No problems using it on plastics/etc. but I try to keep it off of both:
-glass, just a case of being extra-cautious and I don't make a big deal out of this
-aluminum trim, lest it get through a microscopic flaw in the coating and cause clouding/etc.
IME the decontamination systems are very easy to use, even on larger vehicles, and they do a good job. In some cases I clay while the acid is dwelling, which makes for a more aggressive decontamination (but it does eat up the clay rather quickly).
Seriously, they sound a lot more potent than they are. I wish the acidic step was *stronger* than it is. But you should still wear gloves and, more importantly IMO, eye protection.
I can often get by with just a claying *IF* (big "if") the ferrous contamination is just stuck to/in my LSP. This isn't unusual with heavily layered KSG. But in most other cases my experience is that the decontamination effects a much closer to permanent fix. Not always necessary, but worth doing when it's called for.
FWIW, I do a full decon. on *every* new-to-me vehicle, from brand new cars in-the-wrapper to very used beaters. It makes for a nice, clean-slate starting point.