you needn't worry about glycerin soap attracting moisture. You misunderstand the process. Soap and water are used to wash one's face. The idea is that a bit of glycerin, or any other form of oily lubricant, will help seal in moisture in the pores of skin.
Actually folks, you might want to re-think this.
I have long been well into my Oil of Olay years (hey, it’s for “skin
over 25” right? gotta believe that advertising…) and am a
cheapskate so I make my own cosmetic products.
Glycerol is a byproduct of traditional soapmaking - the fats and lye
are combined, and glycerol, which is in fat, is removed (though
sometimes left in, in higher grade products). Glycerin is the
commercial marketing name.
Here’s the important part: Glycerin is hygroscopic – it draws
moisture from the atmosphere (leave a dish of pure glycerin out and
it will eventually become a semi-solution of something like 20%
water; ever use Neutrogena bar soap? what does it look like after a
day or two on the dish? beaded with moisture!). So it DOES NOT seal
in moisture (you can’t seal open pores of the skin or you’d have a
big problem), it attracts moisture, yes, and thus makes your skin
feel dewy and lovely and not so old and wizened ;').
But then by extension, glycerin on your tools will attract moisture.
If you use commercial glycerin soaps, then the oil in the soap will
help counteract the moisture’s effects especially on ferrous metals.
I don’t think the glycerin is needed in the application we are
talking about – reducing friction/heat. I think all you are looking
for is something easy to use to transfer the heat – pure oil is ucky
on your workbench, and so liquid soaps are convenient.
Unless you want to use the glycerin products so your tools look
younger too.