Verdatum: I love your wiki I go there quite often
I just tested making "bondo" thanks to it and it seems to have worked for my purpose.
In the bottom pictures (which flash has really ruined, sigh) I am wearing a mixture of make up and PAX. The black is pure PAX (1:1 PA:acrylic paint) and the colours are mixtures of mica powders and alcohol gel that had evaporated leaving a damp powder.
I have just made a mix to eek out the last of my PA (I need it for my latex appliances) and I mixed it to about 1: 1.5 PA:liquiset with pigments and paint to colour. Too much pigment though and they don't all get set and you wind up staining everything- your paint stays put still. This is why Acrylic paint is so useful as those pigments are already caught in a sticky medium.
It is indeed sweat proof and budge proof but not as much as with PA, naturally. Though the mix I have just mentioned really is very budgeproof! I tried it last night and it would not come off with soap and warm water in the sink and took a fair bit of scrubbing with a scrubbing mitt! But in a shower with the hot water continually running, or in a bath where you can soak it comes off much faster- your body perspires much more rapidly so it lifts off from underneath.
Mixing with the liquiset also reduces the tackiness by a great deal.
The paint I use is students art acrylic. The medium it is carried in is cosmetically safe (acrylic is the base for both PA and Liquiset) but some pigments can be toxic- less so for known brands but there are a few issues with paint on kids toys that have made it to the media in recent years. The brand most commonly available here is Chroma and they do a few different ranges.
For Samara I also adjusted the colour a little as my contact lenses have an aqua tone and it would have clashed badly had I painted myself a warm-dull blue as she really is. The joy with Chromacryl (the student paint) is they have warm and cool toned primary colours to work with
I found I was able to do a base of flat blue then shade with eyeshadows/mica powders dry and damp to get toning.
You can see that it did rub off by my collar; solid resin piece, not recommended! But I also missed the back of my neck here
This shows the shading I achieved over the base colour a bit better
And edited to add: I like to use a brush as it seems to make the application much smoother. For Samara I used a brush that is the same shape as a foundation brush and it just made the painting wizz by. I have used sponges but I find that as they absorb liquid they can make it harder to get an even coverage- possibly because the liquid being absorbed means the paint is already drying before it gets on.