As with any type of refurubishment, if you don't prep the part correctly, the results are not going to be satisfactory.
I prepped mine just like you did, and it still bubbled. Maybe the problem is that the vinyl expands and contracts at a different rate than the aluminum back plate. The originals are some type of photo transfer process, not a vinyl overlay. The first time i noticed the bubbles was after a HOT day at a car show when the car sat out in the show field all day.
With all the $$ i have in my instrument cluster, i did not think $159 for both bezels was an excessive $$ number...but then again I'm so used to paying thru the nose for e-body parts, nothing surprises me anymore. $200 jack hooks, $3100 steering wheels, $1200 parts books?
? LOL