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.
Rescued 22.5" OTS. SJS Mini-WSM. HEB briqs (rebranded Royal Oak). Pecan/Hickory/Cherry/Apple/Peach woods.
2016 Fuji Absolute 2.0 LE (for burning off all the great BBQ)