I'd wrap the breasts in butter soaked cheesecloth, then smoke at a high temp, like 350. Since breasts are so lean, they tend to dry out, and turn rubbery with low 'n slow.
Modded Brinkmann Gourmet. Basic UDS. Rescued 22.5" OTS. SJS Mini-WSM. Stubbs. B&B Oak Lump.
Cannondale 2009 F8 (for burning off all the great BBQ)