Digital painting is pretty hard to master as you need to know special techniques and practice a lot in order to get the result you want. It is much easier to draw something with your own hand, given the fact that you can actually do that and have certain skills.
The good thing about digital painting is that you will simply need special software like Photoshop for instance, and the right brushes that are included in it. Once you have all these, you will also need to know the special techniques that need to be applied in order to get the effect you want.
There are a lot of tutorials, including video tutorials that can give you directions, but in the end you will have to practice a lot, because these will teach you do something by using just samples.
These tutorials will help you learn how to paint in Photoshop and will give you tips what brushes you should better use to achieve certain effects.
Digital Art Painting Tutorials
Making of Three Lines
How to Draw a Digital Portrait by Joshua Bolduc
How to Draw a Realistic Eye by Elna Bastiansen
Making of the Lady Bird by Sophia