I got my Freeze set to 5* the other day so I can't wait to properly test the Freeze set on the Sentinel
I'll also add info on the Gunner Bomber Boy then, but I don't have the character and my recs are guesswork (however, I can't update the title to include both :/ )
He looks incredibly Multiple Attribute Dependent though: MAGIC for his Bomb, HP for his True Burns, DEF for his Decay... Also he has no use for SPECIAL despite being a Gunner.
Probably give him 2 Fierce Iron Talismans for the red slot, and either Bulwark (for MAGIC and HP) or Onslaught (for DEF) type Talismans in the yellow one. Your best bet for blue Talismans are probably Power, as they up 3 necessary stats. Maybe he's a good char for Thief of Invisibility Talismans since he has no use for SPECIAL anyway.