Hint 3: Make sure right edge of line of sight follows the wall.

I use my monk to gather all the mana, including the shroomites. While gathering I place down the aura's.
Place the 4 DU physical wall, on the remnants of the former wall north of the crystal (it barely fits).
With app in place down all DST's and the fireball, use remaining mana for LT's. Add TB as second char and start wave. Drop enough mana for app to build remaining LT's then start TB.
During waves after that I swap my app out for Initiate Boost and boost/upgrade the tower stack (upgrading for me is not needed but could be for your stats).
Final wave I swap intiate boost for my barb then add another char to replace initiate boost again. So for final wave its Barb/TB/IB, since this is a Rad Coal farm it's wise to use different steam accounts to fill each role, otherwise you will just get 1 coal per run. 
As barb sell 1 LT and place a DMG Totem on hint 2 and upgrade that to max. Then just TB and IB whole wave (I cut both boosts short so I dont have to wait for the cooldown for bosses). 
For maximum safety for bosses you can place your TB down on hint 3, make him TB and HB, let initiate boost and then simply hawk bosses down.