Yes, the release agent is the key, and also no areas that would naturally begin to wrap up around a curve as you don't want to have it on so many places that you cannot remove the stock when you are done. Thinking of a circle O - you would only want it all on the bottom half, none up past the mid-line horizontilly, or you will not get the barrel out of the stock without breaking any that is above the center off or breaking the stock.
When it comes time to free-float the barrel, when you know the barrel is set properly, carefully scribe along the barrel on both sides where it sets into the wood. I would run a piece of masking tape tight and even along the barrel just in line with the top of the wood on the left and right sides of the barrel. Then, using a compass, carefully scribe a line about 3/32" (just over about 1/16") - as the line will be your guide for how much wood will be removed to make the barrel free-floating. Remove the masking tape when you are done scribing, so you can see how the barrel is fitting into the newly-sanded stock.
As for whether to free-float before or after the bedding, I am sure there are ways to do it either way. You may want to do a bit of free-floating before the bedding, then continue to finish the free-floating job after the bedding is all in place and you know the barrel is tight to the bedding! Using a short piece of dowel or broomstick handle, etc. (approximate same diameter as that of the barrel), and course sandpaper (like 80 grit to start out), tightly wrap the sandpaper in a U - fashion tightly against the bottom of the O of the stick and with the barrel removed, begin sanding down and out to the lines you have scribed. If you are removing too much wood, causing the finish to begin chipping, go to a finer paper (the higher the number, the finer), like 100 or even 120. The problem with the fine paper is it takes a while to remove a lot of wood at once whereas the courser grit will make short time of it.
Every so often, blow everything off and wipe any grit off and try the barrel, being careful if there is any grit that you don't scratch the barrel! You can try different thicknesses of paper, or several dollar bills to make sure you are removing an equal amount from the bottom as you are from the sides, out to the marks you scribed. Also, looking from the muzzle end at the marriage of the barrel and stock, you should see an equidistant space all around the sides and bottom where the barrel lies in the stock!
If you are meticulous about keeping the work area clean and are careful not to lay the barrel or the stock onto anything that might scratch it, you should do just fine! When in doubt about something, STOP and do not continue until you are sure as to what it is you need to do! Better to wait and do it right than plow right through, ruining the job, your stock and/or barrel!
When completely done sanding for free-floating the barrel, I seal any bare wood that is hidden under the barrel with several coats of clear polyurethane finish so if you are ever in the rain or even a humid climate, the wood will stay dry!
You will probably want a Dremel so you can use the round ball cutter to cut grooves in the area where the receiver lies, so the resin fills the whole area, and also goes down into the wooden stock some. Be REALLY CAREFUL with the Dremel! One slip and you can really do damage to the stock in a hurry!
In some small places, you might need to build like a small dam to prevent resin from going places you don't want it to go, or stuff the area with something and then tape over it. I am thinking of the magazine well. The magazine well box (sides, as one metal piece), you will probably have out along with any floorplate and trigger guard while you are bedding.
You are going to want a way to tighten down the barrel to the newly-poured and applied bedding. If you want a really good job, look up Pillar Bedding:
http://www.google.com/search?hl=en&...m=isch&source=og&sa=N&tab=wi&biw=1263&bih=610
With that, where the fasteners are that secure the barrel to the stock, there are metal tubes that you use that prevent being able to overtighten barrel screws thus crushing the wooden stock (on the underside).
Instead of pillar bedding, the way I got by that was I used some bedding material on the bottom of the stock where the trigger guard is - at each fastener location which secure the barrel to the stock (on some guns, also where the magazine bottom trap door is located).