1. Both Liquid and Pencil eyeliners have their use. I use mainly powder makeup. Alexa Poletti on youtube is an absolute doll and her hair/makeup videos are a good starting place.
If you like the factory makeup, take good clear photos before you alter it.
2. On dolls, you don’t have to worry as much about foundations/concealer/cover-up because the doll’s skin should essentially be perfect. Although, even on dolls, I recommend using a primer when trying to make bright colors pop.
Dissimilar to humans, if you want a realistic face-up, you have to be careful how you add contouring, blushing, freckles, moles, and etc. It’s easy to overdo it, but no contouring at all may make her face look flat. Particularly with cheaper TPE girls.
Higher-end silicon girls tend to have simulated pores which affect how the application looks. Some will have blushing already as well which you can’t hide UNLESS you use concealer, foundations, etc. This could be a good or bad thing depending on the project. You can use less product on Silicon girls as they tend to NOT absorb the product as much as the other two types.
TPE girls’ skin is usually very flat so you have to manually blend in color gradients carefully. They tend to absorb pigments so gradually building up your color is recommended for them.
I use baby oil to erase and sharpen lines on all three types.
I like matte finishes so I use powder for most of my applications. If you want shiny lips, you can use glazed lip paint with success. Be careful using liquid form products, a little goes a LONG way.
The most important thing about doing makeup is making sure you have clean lines and consistent, even blends.
Learn how to make up your sex doll from here.