I went ahead and ordered a Dovetail cutting jig from DGW along with more of their browning solution. Yes, it would seem that this jig could be hard on hacksaw blades & files. But as you stated earlier, hacksaw blades are cheap. So aren't 3-cornered files on ebay, e.g. slim taper & extra slim taper. I have cut dovetails for sights & barrel lugs on 3 barrels without a jig. Everything worked out well but I always wished they looked a little cleaner. Just my OCD kicking in I guess.
It does pain me (my wallet) to buy single purpose tools. But . . . it makes the money spent so worthwhile when the job turns out really nice. Whenever possible I make the tool/jig needed. I looked at the safe/dovetail file at Brownell's. I'm sure that to many it is worth the money ($45.00?) spent. If I couldn't make one then I would buy it. But, in this case, I can make one as good as that in a matter of minutes. The "taper" on a regular three cornered file only encompasses the the last 1/4 of the file. I cut it off. I grind one side perfectly flat on my 6" disc grinder, making sure the radius on the two corners is gone. Easy peasy! But then I am fortunate in having the tool (disc grinder) to make the tool.