on the one i just finished (and the three i'm currently working on), I did not use any glue - just stitching.
I attached the gusset to the pocket front by stitching the edges back to back.
Before stitching, i marked the edge of the gusset that would be joined to the body of the bag - NOT the edge joining the pocket front. As you say - that would be backwards!
I measured the centrepoint of both the gusset and the pocket stitch line and worked out from the centre in both directions so i would be guaranteed the same overlap at each side . The only marking was done on the front of the pocket.
To ensure it was all lined up, i had traced the outline of the pocket onto the gusset with a light scribe and used this as a guide to hold the gusset against as i punched and stitched each hole with the awl. Clips just got in the way for me, and the parts too bulky to use a clam so this was all hand held whilst the stitching was completed.
Going around the bends was just a case of ensure the two edges were aligned before pushing the awl through, and only making one hole at a time and finishing the stitch before moving on.
For me, it made much more sense to attach the gusset to the pocket BEFORE attaching it to the main bag front, before fitting the bag front to its own gusset. Essentially you want to avoid stitching into an enclosed bag as your hands and needles will find it much harder to do anything, especially if you have chunky hands! The main bag gusset was the final part i attached.
What i'm thinking might work even better - although its untested until this weekend - is to mark the stitches on the pocket front panel, and before attaching the gusset, use those holes to mark the stitch positions onto main bag front with awl , then when you have attached the pocket and gusset and come to attach the gusset to the main front, the holes marked on the gusset edge should line up with the holes made from the pocket front template.
good luck.