Thank you all for the kind responses!

JMac, thanks for the additional info on the effect on existing putty/primer work.  I'm not surprised, though, given how it works on paint, clogged drains, dirty ovens, etc, etc,

Seriously, I'd long read about using automotive de-greasers, and even brake fluid, but what caught my interest with this product is that it is relatively benign, compared to things like oven cleaner, or lacquer thinner.  You still should wear rubber gloves--I use a pair of kitchen cleaning gloves, for example--but it's not nearly as caustic to use.

For folks outside the US and Canada, you can probably find similar products, with similar ingredients.  I got that question over on the Treefrog Toy Soldier forum, from one of the members who lives in Singapore.  I will post the ingredients, for anyone who wants to find a similar product.