I have used a mix of lump and briquettes for my last three cooks and I love it. 6 to 8 Briquettes to start the fire and monitor the temps on the way up and like N8man says 10º before your target temp is where you want to fine tune your air intake. I use magnets over my intake holes and can see exactly how much the holes are open and can adjust from there.
You would be surprised at the difference an intake hole only open 1/2 way verses 3/4 way open makes on the temp.
Your Tenderloin turned out great so I'd say don't sweat the small stuff and keep getting BBQ on the UDS experience so you can play your smoker like a Stradivarius violin.