Frank, I think they are referring to taxidermy.net. Matt (KMA) did a tutorial on injecting feet, but his method also removed the feet. If you are not going to remove the feet, tie off the top of the leg where the skin meets the feather. I wrap mine in yard, to absorb any extra master's blend that does indeed pass into the cavity of the bird. With the yarn wrapped around the leg and wire inside the cavity, it does help with keeping this stuff off the feathers.
Since everyone is throwing in their advice I will give my method. I do not cool my master's blend. If I had a fridge just for that, I would, but it will stink the thing up to high heaven. So mine is at room temperature. I just add part "A" and then part "B", using two different syringes. I use the same injection spot for each liquid, but I don't overfill with the first injection. I add an equal amount with the second injection, and massage the toe, foot, and heel as I add the second solution. It works for me, but I don't know of anyone else doing this method except for people that were struggling, and I gave them my thoughts, they tried it, and liked it. Many people I know are struggling with too quick of kick times, but either they keep on struggling, improvise by cooling the stuff, or try something else. My method works well. I don't have to keep it cold. I have a longer time to inject, and work the feet, I get no cross contamination, and I can use a syringe for at least ten ducks before it is no longer usable. I keep each solution in a separate 10 mil bottle, and pull off the needle and suck up five mils into each syringe of each separate solution, and then put the needle back on. Tip the needle upward, and squirt out the air onto a paper towel. Add equal amounts, and you're gold. After I inject, I will squirt acetone on the feet until the liquid coming off is clear, and not milky. I card after that. If it is a standing bird, use Pat's advice and make sure you have something to keep the solution from getting on your base the bird will be mounted on. Flying birds will be fine, but have a acetone-wet towel to absorb the stuff that does indeed come out of those injection holes, while you are injecting. Clean up is done with acetone or lacquer thinner. I prefer acetone.