Resin is not actually a flux .It is used as a barrier to prevent oxidation when soldering previously tinned parts . I have laid ribs using old fashioned irons heated in a muffle and drawn down the bores . This is method is Ok And is great for "flushing down " but most people now-a-days use a propane torch , however care is needed not to over heat as the resin just tends to burn thus negating its purpose as well as having the solder run out and leave misses . Never tried an electric iron and I would imagine that you would need a pretty big one to get the spread of heat needed . Each to there own and having laid/re-laid close on 140 sets of ribs last year I will stick to my tried and tested ways .
