|Concealers are either yellow-based or green-based.|
The answer wasn't to layer on more and more make-up.
She said to start with a silicon-based primer. (Yes, it sounds like painting a house.) This puts a layer between your make-up and your skin. It protects the skin from having any reactions to the make-up (so it means your make-up shouldn't aggravate your rash), and also helps the make-up last longer.
The next thing is to choose the concealer colour you really need. I always thought concealers were supposed to match skin tone. Actually they're meant to be the opposite of what they're concealing.
Concealers are either yellow-based or green-based.
Yellow-based concealers are to cover things like dark rings under your eyes. Anything dark, and that blue-black colour gets covered with yellow. The darker the colour, the more yellow the concealer needs to be.
Green-based concealers are to cover red, so red rashes, broken capilliaries, any red marks at all. Again, the darker the red, the more green the concealer needs to be.
You don't need tons of concealer, just the right shade. The cheaper brands of make-up (which I usually use) don't give a lot of choice, and usually just have lighter and darker tones. So for those of us who really have something to conceal, probably need to get high-end concealers which are categorised according to how yellow or green they are. (Even if we keep using our $5 make-up apart from that.)