The trick to better duct sealing? Better planning and glopping it on thick
After you've figured out the duct configuration of your ventilation system it's time to seal the seams with mastic. But for sections of the duct that are removable by all means remove them and set them on your workbench.
It's easier than squatting around in a mechanical room and you can do a superior job keeping air where it's supposed to be.
For ducts that must remain in place, take your time and glop it on thick.
—This video tip was shot on the jobsite of the 2017 Model Remodel featuring Ben Bogie.