Since 2010, Vent Cap Systems' reusable air vent covers have dramatically reduced the time needed to set up a Duct Blaster® for duct leakage testing, however, still having to tape the return air side has remained a huge pain point. Both DucTesters by Retrotec and the Minneapolis Duct Blaster® by The Energy Conservatory come with a plastic 'round to square' flange to attach their calibrated fan systems to the return air grille via flexible 10" ducting. Applying enough tape to attach the flange, and to withstand pressurization, requires a lot of time and a lot of tape so for decades, people have developed "work arounds" but none are perfect.
I'm hoping to launch my long awaited return air solution at the RESNET Conference in Scottsdale, AZ late this month (Feb 2016). Sign up below and I'll send you some of the "work arounds" that people have been using, the different iterations my design process has taken over the years (including the one pictured below), and you'll be among the first to see it in action.