I recently had a Breyer Strapless come in for finishwork. Sadly, the poor thing had suffered a mishap and the owner attempted to pin the leg to repair it. By pinning I mean holes were drilled into each section of the leg and a metal pin inserted and secured. I've tried that method before and had a horrible time trying to drill the holes deep enough, securing one end and then trying to align the pin into the hole in the other piece and somehow getting it all to stick properly. Ugh!
Awhile ago I read about a different method of securely repairing a leg and I decided to try that. It involves Dremeling out a trench and putting in a pin and securing it with soda glue (baking soda + super glue).
The first order of business was to Dremel a trench. I super glued the pieces together (so I could get a nice, straight trench) and then very carefully Dremeled out a groove in the thickest part of the leg. Of course, the super glue didn't hold very long, but it held long enough to get a good start on the trench. After I got the trench long and deep enough to accommodate my pin, I re-glued the pieces, lining them up as carefully as I could.
Then it was time to insert the pin. For that I chose to use a screw that I cut the head off of. Other people use nails or other pieces of sturdy metal, but I thought a screw would give it extra strength and "grippyness". I chose the screw before I made the trench, making sure it wasn't too wide for the leg (the head was too wide, so I cut it off using a vise and a coping saw).
The next step was to secure it with soda glue. I dropped in some super glue, sprinkled baking soda generously, carefully patted the baking soda into the super glue and let it cure for a day or so.
I continued adding layers of soda glue until the trench was nearly filled.
Once it had cured (I left it sit for a few days), I sanded to remove excess soda glue, washed the area well and used epoxy putty to fill in the remaining depression and smooth over the seam lines.
And that's pretty much the gist of securely repairing a leg, but I imagine this would also work for tails and on resin models, also. Good luck!