Exposed/ External seam purse

[Scifidelity]

Howdy folks. New guy here. I've been doing leatherwork as a hobby for about 3 years. 

Context:

I have a Cowboy Outlaw machine. I mostly use size 207 thread, but also have 277 and 138, but the Outlaw doesn't like 138 much. I just finished up my first purse. I used size 207 thread. 

Question: 

I'd like to hear detailed tips on how to best execute external seams on bags. I tried all three walking feet (double toe, left toe only, right toe only) and really struggled to keep the two pieces of leather aligned. I tried gluing them, I tried seam tape, etc. I'm open to anything except doing it by hand . I'm also not going to buy a post bed machine with a presser wheel, YET. 

Edited February 26 by Scifidelity
added

[Digit]

I got taught to use contact adhesive, then sew with a left toe walking foot. The CA should keep the pieces aligned. Do use contact adhesive and not PVA/white glue or something. I haven't used double-sided tape for leather seams yet (I did get warned by my teacher to never sew through tape though), but from experience elsewhere I can imagine it would more easily come loose than CA while manipulating the leather when sewing.