I use a sno-broom(foam pad used to remove snow from cars). i push thethe bunk end sides in all the way till the roof vinyl is lying flat on the beds. then lower the top about half way then tuck in the sides as far back as they can go. then lower the roof all the way.  mine has loops on the bed bows so it pulls the bunkend canvas with the bow when you lay it down but im scared to tie it to it. too much tension on the fabric. i usually end up with a single crease on my side panels right in the middle. mine is getting a few years on it and trying to make it last.

Funny you should mention this.  I had trouble getting it pushed in evenly when the top was almost all the way down.  If I don't push it back in as far as it goes, I have to lean on the top with my elbow to latch it.  I made a tool for it.  I could have probably made a small fortune (at last 5 dollars) by getting a patent, but I put it on here cause I like you guys.  🙂
I'm not sure how to reference the link, but go to the forum on here for "Pop up Campers", then go to "Canvas tucker".  I took the pool noodle off because it sticks.  I also unzip all 4 corners and fold them in.  Happy tucking.

I have a special (made for me) tool I use to tuck most of my canvas. It is a pretty tool, and a sweet one at that. It is called

MY WIFE!!!!!

While I lower, she walks around and tucks. When I am 2-3" from all the way down, I stop. She tucks big side and back. I tuck door side and front.  DONE!!!! very simple very easy.

We use the same method as LoneLock did, it's always worked great except some people were a little too vigorous in shoving everything in which resulted in tears to the screens (easily sewn up, but I still would rather have spent that time doing something else...)