WildatHeart
I use both methods, solder on the front sight on a trade gun or fowler and dovetails on rifles.
I use 95/5 solder when soldering, and use a hacksaw to remove most of the metal to proper depth for a dovetailed sight then remove the metal between the hacksaw cuts leaving a shallow square or rectangle cut out in the top of the barrel. The dovetail angles are filed in using a fine triangular file that has had the cutting teeth on one side smoothly ground off. The smooth side of the file is placed in the bottom of the sight cut out and the corners are used to do the undercuts for the dovetails to get a snug, wedge fit for the sight.
Hope this helps.
Regards, Dave