Yeah, people methods vary. I used to use the "build up bit by bit method" but now I use the subdivide and get in there method, but tbh it's starting to change to a combo of the two methods, as I incorporate my own.

I think a big problem as to why your modeling is looking off, is because of the anatomy/proportions are off. It's not looking that lumpy, just the weight of certain muscles are off.... such as the pecs.

As for you question about how much details to add... well that up to you, but a good starting point would be to add as much as you current subdivision level can support.

Though i will be honest, I've found that the best way to get nice smooth wrinkles (clothing, skin, folds) and nice sharp details and insets, is to use the standard brush with a sharp alpha. Or curve. Also building up transitions between forms it's best to use a nice flat (square) alpha/curve.

Sorry, but I'm not that familiar with MB... only ever used it once.

But your brushes look fine to me.... but I'm using MB09, and the brushes are different in this version.

All, I can say is experiment with different brushes, but you should be able to achieve your goals with the standard brushes.

Also, now that your getting into anatomical sculpting, and such, try to really focus on learning the anatomy.... not that you don't know it now, but you know what I mean.

Also, CGArena.com has some brilliant sculpting tuts, and time lapse videos.