If I am reading everything correctly, it seems that most rust convertors (metal ready, prep etc.) are just phosphoric acid. Any idea where to buy this product in the Calgary area? Can you just paint following the application? Thanks.

 

Been in the body business over 6 yrs now and have used all types of rust converters or cover over items, none of them work long term.
Bottom line nothing works like a good spot(sand) blaster and some epoxy primer.
Make sure to sand blast all the rusty area, then apply epoxy primer to the bare metal. Once the epoxy primer is dry then you can fill or fibre glass any of these areas.