Don't be discouraged if it takes several attempts using this method. The coin has to be warm enough to loosen the hide glue or whatever they used to set them but cool enough for the hot glue stick to have a good set. It took me several attempts on my current restore. I suspect that buying some high temp hot glue sticks will solve that problem.
Also, be very careful when resetting the coin. I ruined an aluminum coin by using a grade five bolt head as a driver. The three slash marks made dents in the coin. I have since found a better bolt head and did some grinding on it to remove any high spots. In the future, I probably will also do a careful cleaning of the opening so that the coin slips in with finger pressure. I usually reset the coins by shaving a little bit of hot glue into the opening, placing the coin over it and then using the hot bolt head to heat the coin and press it in until seated.