It's pretty easy - I saw a former Volvo tech do it on an Ocean Race. Pull out the door seal rubber on the body near the top of the trim piece so you have access to grab the upper edges of the trim, pull it out/away from the pillar towards you (like if you're sitting in the drivers seat), once it pops off don't pull it off completely because you can break the plastic clip holding it in place. If you reach behind the pillar trim which is still attached (you'll have about an inch to 1.5 inches gap) you can turn/rotate the little plastic clip so it can easily come out of the hole in the pillar.I'm curious as to how you removed your pillars. The fabric on mine is starting to peel back and removing the pillar to re-glue it would be a lot less messy than trying to do them in place.
This is excellent advice. I used the super 77 when doing a headliner on my old 850. The headliner material had a foam backing and I noticed when I pressed down too hard when applying, the super 77 would soak through the fabric. The fabric on the pillars in our cars is so paper thin that you can guarantee it will saturate unless you wait for it to tack. I did not wait for it to tack and I had to re-do it with another sheet of fabric.One mistake people make is to spray the adhesive then immediately lay the fabric back down. NO. DO NOT DO THIS.
The key with the 3M Super 77 adhesive spray is to spray it on to the pillar where the fabric has pulled away, then also spray it on the back side of the fabric as well. Once you've done this, wait a while, even a couple of minutes and let the adhesive become tacky on both surfaces, pull on the fabric while laying it back down and rubbing the fabric back into the trim piece. For the best results find something to lay on the part to hold the fabric in place so you don't have to stand there hold it forever.