Not exactly a tutorial but a useful tip for creating polygroups.
When you have a model that has hard to reach polygons which you want to group, what you do is create a morph target, shift polys around so you can easily select the polys for the group then when you have finished grouping, you switch and delete the morph target. I’m pretty sure this can be used for other functions, too.
Cheers,
Revanto 