Replying to Studio Portraits - help

So i got myself a little job shooting staff at a local insurance company (30 people)

i was wondering if any of you know how to make a cheap soft box (that can be mounted on a lightstand)

i have 2 SB-900s, 3 PWs, D300 and stands that i will be using for the shoot.

all my studio stuff has all been creative and "artsy" but now i have to get down to professionalism
so yeah, i generally know how to shoot studio portraits, but i would like to use a softbox or any type of diffuser. i dont have much money to spend.

HELP me photographers of NS. tips, what to do and dont do. etcetc

+K for anyone who helps me.

Thanks in advance