TheArtistic_Division this is mostly for you since you asked lol
First step is to make an outline of what you wanna draw

then choose around 4 colours to shade with

use the middle colour to fill in the main portion

i know it's messy but you can clean it up after.

now you're gonna have to take the darker colour and line out the darker areas...

now do the outlines with the darkest colour. ( try to refrain from using black)

Repeat for highlights with lightest colour

Now you're gonna want to find a blurring tool to mix it all together! If you need too, pick the colour you're blending and set the opacity to low to help the mixing.

im gonna finish it but just keep adding and blending til you like it! (Ps. Sorry you can still see the underline... my layers got all messed up and i usually do everything in one)

Bye! :D