What you will need:
three rifles (preferably AK47 or Gail AR)
How to execute:
Have your AWP go a-long and distract, preferably thow a smoke as well as a decoy or two.
Have your shotgun go in lower tunnels through mid and clear upper tunnels
Your SMG will stay in mid to rotate and help out where needed but will never leave the general area of mid doors, and will be the bomb carrier.
One rifle will go through mid doors and hold, preparing for any rotating terrorists.
The other rifle will go up cat, attempting to clear A site.
After A site is cleared:
Shotgun will rotate back through T spawn to long, throwing a Molotov while backing out.
Mid rifle will rotate to A through CT, making sure to cover both B doors and window
Cat rifle will stay at site, covering his advancing teammates.
AWP will move to to goose
SMG will move through either CT or cat depending on where the pressure is and plant at A.