There is a Fashion Beauty & Makeup section on CDH. My guess is that often by the time folks show up here, often they have been crossdressing for a while and have picked up some degree of makeup skill. But, that doesn’t cover everyone.
As far as getting the right shade for makeup, my suggestion would be to talk to a Mary Kay person. My first wife was a sales person some time ago. They were very particular about training the sales personnel how to determine the right shades. Hopefully they still do. When they are selling, they have to be pretty much self sufficient as they are not in a store with other personnel and surrounded by tons of product.