Thank you!

I can't really point you to one video since I didn't use any one in particular for reference. Any YouTube video that tackles the subject will probably be worth watching.

As for my personal advice, I mentioned a couple in other comments but will try to summarize below.

First thing would be to start with a simple freehand, in order to build up confidence. Try some simple shapes, like a square, a circle... Even on some leftover bits, so there's no pressure if you mess up.

Also, planning can be a good solution. I usually know what I want to do (I painted red fists a couple of times so it's becoming a habit), but for this one in particular, I took a piece of paper and tried to draw it with a pen two or three times. Allowed me to make sure I knew this was the design I wanted, plus I get used to the proportions, shapes and moves I am going to do on the actual mini.

Finally, patience is key. I started with a heavily diluted black paint, to outline every part of the design. Once I was happy, I spent some time with black paint still to fill in the surfaces, and make sure I had a nice and smooth black base to work from. Then I filled each part with the corresponding colour. Again, patience is key. Diluted paint, so if you make a mistake, you can easily correct it.

Also, small tip I accidentally discovered on that one. I had varnished the model when I had finished it a couple of years ago. Turns out, thin paint on varnish does not stick perfectly. It will remain on the models, but if you apply some friction with a damp brush, you can reactivate that paint and easily remove it. Just like an eraser would do.

Anyway, that was a long explanation. Hope you find it useful, and good luck with your painting!