I was thinking this out the other night to help out builders wanting a better looking weld line. Since most are using some type of 2 part epoxy putty, I think this will really help out.
First you'll have to make the tool. I used a little piece of aluminum I cut to about 2" x 3/4".
About a half inch from the end, drill a hole in the center line about the size of the bead you want the weld to have. I used a 3/16" bit for the bead around the n-filter. Smaller sizes for smaller beads like around gun handles. Then trim off the excess according to the image below.
Next you'll cut a small section of the epoxy. I have the kind that comes rolled together and you just gut a section off and mix together. Work small because time is short with quick epoxy. About an 1/8" section is enough.
Roll a little snake about the same size as the hole (3/16") and press it onto the edge where you want the weld. Compress it down to about half its original diameter making sure it holds weld to the [clean] surface. Press down along both edges to almost flat with the surface. Wet finger to avoid lifting the epoxy.
Take the tool and quickly start at one end of the line and push down at an angle of about 15-20 degrees. Move up about 3-4 mm and press down for another bead. Evenly repeat all the way down the line. If the tool sticks to the epoxy and lifts it, just keep a little wet sponge to moisten the tool after each press.
As the epoxy is starting to harden, use a razor blade to trim excess epoxy from both sides and use your fingers to press down the edge to blend it into the surface on both sides of the line. Use the tool to retouch any of the beads if needed.
Make sure to work in small sections to avoid the epoxy hardening before you finish the process. About 2" lines.
Now for the illustration.