i have a hairy stomach... so when i blend it in its fairly simple as i said, just kinda of follow the V of your pelvic area... it not only blends in nicely, but it also forms a point... almost an arrow, of hair.. pointing down to your gems.. which is a nice feature...
as far as the legs, i do not have very hair legs at all... im glad, and my arms are pretty much hairless.. im actually really happy with that! lol..
so i do not really have any idea on how to address your ball shaving trouble... the only thing that comes to mind that may help is to use the electric buzzer... if you get a nice one, it should come with many different attachments for different lengths, i would start with the lowest in all your pubic area.. then the next step up attachment u can do ur thighs very close to ur nuts, then the next step for a little farther now ur leg, and so on and so on, untill it "fades" and blends together....
on your head, that haircut is called a "fade" when its somewhat long on top, then fades down to nothing down below ur ears...
so i can only imagine this style could help with your hairy ass legs, as far as your bum goes.. i would not put much thought or effort into that, while your sitting on the toilet bending over and seeing ur nuts and bum area, whatever u can see from the angle is all i would really worry about... i mean, how often does the girl see ur butt?
unless you are into some very kinky, strap on sex, u should have nothing to worry about.