when i did my b-pillar using dinoc CA-421 4yrs ago, i did not use primer to wrap it around. just cleaned it up real nice using motor spray, and tucked it under as the op did on his DIY.
i do plan on removing it some day, so did not want the near permanent bond.
on the other hand, when i did the 3 switch trim on the center console, i really could've use the primer's help.
stayed on nice after like 10 heat cycles though.