My fam loves chicken, I do boneless skinless thighs and breasts all the time. I have found that the Traegers don't really crisp chicken but I get great results by going hot for the whole cook. Many have told me it's the best chicken they've had so I'm in the ball bark.
I have done this countless times over the last 8 years, first on a Traeger Junior Elite and now on my Timberline.
I rub the chicken parts, it's fun to experiment with rubs for sure! My wife likes more herb flavors and I like the red spicy blends. I pull the chicken from the fridge, apply rub and let them sit out and covered for 45min-1hr.
I heat the grill to 460F. Bottom grate, at the 2" raised position, my grill is hotter on the left so I put breasts there, spray oil on grates before dropping chicken.
Breasts take 15min per side, thighs take 10min a side, So I run a timer and use this sequence to cook everything in 30min;
1- Drop the breasts, and set a timer for 10min
2- Next Drop thighs, set timer for 5min.
3- Flip Breasts, set timer for 5min.
4- Flip Thighs, set timer for 10min.
Probe parts with instant read thermometer, 160F (it's ok if they overshoot up to 10 degrees)
This gets everything cooked and completed at the same time. The chicken looks great, grill marks, and super juicy.
I kept careful notes and slowly dialed the temps to get me the 30min cook, your grill may vary a little but this will get you close.
Report back if you try this.