For this example, lets assume I have:
- Boon Focus II (Bolster)
- Multi-Target Boon Specialist II
- Multi-Target Boon Expert
We will also assume I am trying to Bolster a group of 5 players.
BF2 would give adv3 for multi-targeting.
MTBS2 would give adv2 for multi-targeting.
A multi-target Bolster for 5 targets would be at disadv5.
Since the MTBS2 brings the roll to no disadv, would MTBE cause an auto success?