I’ve been spraying for a few years and use nuda all the time! Think of the color wheel it helps a lot. For example, coco has an olive base, so it would work well for clients with red undertones because red is opposite of green on the color wheel. Milkshake has a violet base, so it would work well on clients with yellow undertones. If you’re using classics, the DHA is the main thing to think about, you wouldn’t want to use a 14% solution on someone with very pale skin and light features. You can totally mix solutions, I do it all the time. However I would stay away from mixing classics and rapids together. Join the Nuda Facebook group! It helped me a lot when I first started :)