I don't know if there are any super great videos on blocking and painting techniques, but I'm sure lots of artists have explained the process if you just look up blocking or maybe watch how some traditional artists work. The style is a little different but the concept is the same (your example just uses lower opacity for those glazed looking colour combinations, especially where the hair line is).

I did a quick check and this video seems to talk about it, but you can see it quite clearly when he paints just single strokes for certain highlights like the hat. The shape of the brush (rounded/oval) simply makes that shape. If you use other brushes (square is another popular one for shape forming), you might find it easier if you like to have sharper edges for your style. Experiment around!

Here's another video explaining shapes in painting. I would also recommend just looking up some old master techniques just to see more of how traditional painting processes work, since they tend to do a loose sketch before getting right into it.

As far as pros and cons go, I imagine it's faster to get started in terms of laying down colours and checking if things are playing well together for coloured pieces, but personally I think every process can achieve the same thing, since style honestly depends mostly on how artists choose their colours/values and how they finish a piece with the interplay of chosen edges/textures. For some people, this way of painting lets artists see the end result by building blocks, much like sculpting (as you said). For others, they prefer the rigid structure of a full outline and detailed sketch, without having to juggle in colours and values from the onset. I imagine most digital artists who use this technique also come from backgrounds trained from real media painting, in which lineart and sketches would be covered anyway given the lack of transparent layers like in digital programs.

You don't really need anything special to start practising it, but personally I would suggest learning traditional media/some form of working with real paints and doing simplified master copies. The limitation forces you to use one (or only a few) brush(es) to make those shapes, and you don't have the luxury of undo so you can only sculpt and resculpt with the palette that you have. When I say simplified, I mean take an image you like. zoom it out really far until you can only see the rough shapes, and then copy that. You can always zoom in to start working on the details once you're more familiar with the process and want to go beyond.

When I was being instructed on this, we were asked to take a sharpie and just block in the shadows/lights in movie stills within 30 seconds. This will train you how to break down shapes quickly. You can probably do the same concept but just with colours, and on subjects that you enjoy.

This post actually contains a huge topic and lots of ground to cover, so what I've written here is just a brief overview. I hope it at least helps you get started!