I have only done a few of these and I'm sure there are better methods of doing it. It is super easy and fast and easy to blend the colors.
First step I do is put a very thin coat of vaseline over a tine that is like the one I want to repair. Then I mix 100% silicone with xylol to thin it. Put a thin coat over the tine that is like the one you want to build. If the one your replacing is broken off at the main beam put a coat out onto the beam of the one you are casting so you have a way to attach it to the beam.
Once that is dry put a nice heavy coat or two on to make a mold of the tine.
Now you need to pull your mold off of your tine and attach it to the area your going to repair. I put a small amount of silicone on the base to help seal it. You can either tape the mold on or use cable ties, which is really easy if it is only part of a tine you are doing.
Now split the top of the mold about an inch. Mix up smooth cast 320 and pour it in.
Let it set and peel it off.
I like to color with thinned acrylics