Barge works if you can find it. So does Aquaseal, but it gets pricey to do it with Aquaseal.
Here's what I do if I'm using Barge:
Make sure your boot surface is as clean as you can make it. It's OK to leave a little felt if its clean and doesn't make a noticeable bump.
Stuff your shoes with as much wadded up newspaper as they will hold to form a firm rigid last. Make sure the new felt is sized to the boot bottom. Any overlap, especially at the toe, will pry at the felt when you walk and then, you'll be putting another new set of felts on sooner than you'd like....
Spread a healthy layer of Barge on both surfaces covering them completely. Use more glue than you think you need. It's hard to use too much and easy to not use enough. The new felts will suck up some glue so use even more on them. Wait 15-20 minutes for it to get tacky and fit felts to boot bottom pressing them firmly into place at all points. Get it right the first time because that's the only chance you'll get..
Put several wraps of duct tape around the boots covering all bonded surfaces several times, Make the tightest wraps you can without distorting book shape. This is where having a good last comes in handy. Just as it is hard to use too much glue, its also hard to use too much duct tape. Wrap them thoroughly.
Go away and leave them alone for at least 12 hours. 18-24 is better, actually.
Remove all the duct tape and go fish.
This is what I do and it has always worked for me...