I there is no binding, i would just use a normal fretsaw (i have an ancient stewmac saw that i resharpen every few years, and a newer japanese saw from LMI, i would use the duller one for cleaning out glue) to carefully clean the glue out of the slots without deepening them too much. If it is bound, a little hook like the stewmac one
http://www.stewmac.com/shop/Tools/Special_tools_for:_Fretting/1/Refret_Saw_and_Fret_Slot_Cleaning_Tool_Set/Pictures.html#details is handy, and easy to make yourself from feeler guages or any piece of steel the right width. I wouldn't mess with a soldering iron on the glue, it scrapes and saws out pretty easily.
Advice about tang width is tricky to give, it takes some experience to know what to do, and when. If the slots have not been overly widened, and you are not trying to induce a backbow, i would probably recommend a standard tang width. I like the stewnmac medium high and medium higher for just about everything, glued in with thin CA.
Basically, a refret is not that different from fretting a new guitar, you just need to be careful of the finish and any issues around funky slots or spongy necks.