Hi Jim
making sure the two surfaces are lined up and held in place and in line, I sprinkle with very fine talcum powder into the the joint, use a fine brush to get it into the gaps.
Super glue on a cocktail stick - touch onto the talcum powder along the bottom edge of the coach, not the front it gets pulled in by capillary action, it does require a fine hand.
Produces a very tough composite when hardened, which can be sanded down and primed.
On the internal side prepare some superglue mixed with talcum powder - it makes a paste which sets fast but you can build a thick, tough layer across the internal seam. Again this is really tough - you may need a Dremel to sand it down
Obviously try elsewhere first before trying on Mentor