Thanks Jim
If you have time and you want a nice neat end result at the fin edges I recommend you don't do all fins at once. I went with it so I only had to do one bagging session and I knew I was going to be coating the edges in high temp epoxy (plus I'm only planning to hit M2.5). I used a lot of the info in Jim's carbon guides - they are excellent and well worth a read (or 10) - and then tailored that info to the process I wanted to follow.
If you do decide to do all three then I would think about the following:
The aeropoxy I used (2032 with the 3660 hardener) will keep the carbon & most of the peel ply in place while you're doing other sections but not the breather.
I used small pieces of tape front and back to keep the main section of breather in place and then when I had both sides of a fin done a small piece over the top from one fin to the other to keep the edges of the breather in place.
I made the bag from three pieces of stretchy bag material - one per section. The 3-way (or 4-way in your case) section at the back needs some support/tape to keep it together through the bagging process. Figure out a way to extend and block off the rear of the main tube so your bag does not get sucked into it (and pull the 3-way join apart). I also sealed the front of the tube (but not perfectly - was losing some air there).
I taped out the cloth with masking tape and cut it so that there was a thin (1/4") piece of tape left holding the edges. Cut carbon cloth frays if you so much as look at it or breath wrong - I have no experience of whether glass cloth is the same.
I then trimmed the front and back of the cloth where it will lay on the body tube before placing it. Then trimmed the fin edges after placing it to minimize fraying. However, trimming as you go lengthens the whole process and makes it more likely you'll end up with stray carbon "bits" where you don't want them. If you only do one section at a time and have a support jig you can trim later for less stress and a cleaner result.
Make sure your peel ply is a bit larger than the carbon otherwise you'll have breather stuck on which has to be sanded after it's all setup.
It took me about an hour from mixing the epoxy to get everything done and under bag. I had the back and sides of the 3 part bag already sealed so I could just slip it over the back and seal it on the body tube ahead of the fins. I also masked out the body tube for a good 4" under where I had the vacuum attachment.
I de-bagged after 4 hours @ 100F (Texas is pretty hot this time of year), removed breather/peel ply and trimmed rough areas with an xacto then left it over night to cure.
Attached a photo.
Zeb