I have used system 3 to build surfboards. It is high quality stuff. It needs a thickening agent to create any gap filling. You can use wood flour, saw dust, microballoons or silica. Laminating fiberglass to wood it can be used without thickeners, but for wood to wood I would use one of the above agents to prevent gaps. Just make sure to mix the resin and hardner well, in the proper amounts. follow the directions to the letter and you will get excellent results. To prevent it drom setting too fast, some people mix it in a flat pan to keep it cool. While mixing it is exothermic (gives off heat) and this heat will hasten curing time. There is no absolute need to cure in a hot box, unless temps are below 50 F. Cooler temps prolong cure time, so the cooler it is the longer I would wait before stressing a glued joint. This epoxy used in a thin or less viscous state also makes an excellent finish. Be aware though that some formulations will be more brittle than oil finishes and may over time show some stress fractures on frequently flexed parts of a bow.
T88 is a good glue for structural bonds like risers, tips, arrow heads, etc. It usually needs no thickening. If the glue joint will need sanding afterward and you are afraid that the epoxy will be too hard to sand, microballoons will make the cured glue easier to sand. That pretty much goes for any type of epoxy.