The Devcon is going top cost you so much more in the long run. Get your epoxies from hobby stores like Hobby Lobby, Micheals, or any Nobby Stores that sell RC outfits. These stores will have your 5-min, 15-min epoxies etc. The thinnest I have used is Bob Smith 20-min finishing epoxy, as it nearly flows like water. The next up might be 30-min, allthough there is a 2-hour epoxy, but I am not sure if it is thin or not as I have never used it.
Should you try the 20-min for instance, and deem it to be too thin, you can in turn thicken it with a product called micro-balloons.
I typically use 5-min epoxy for surface mount fins only, 20-min for laminating composite materials (i.e. fiberglass; kevlar) onto bodytubesn and 30-min epoxy for fillets, and main bonding of structural parts.
The mid sized set of these epoxies cost about $8 and will build many many rockets.
Remember, more epoxy only adds weight, not strength...use only what you need and let the epoxy do the rest.
my $.02 worth...