I don't let it get to red. After shiny blue it will go black. I then carefully and quickly align the "key" and press it into the already carved out slot. It'll go in easy and then stop. Withdraw the key and reheat, then go in a little further. It will likely take three or four of these heats to burn all the way through. You don't want to force it, and though there is some smoke it goes fairly easily, if you have the hole prepared so you are just slicking up the sides and corners. It's to finish the hole, not make it.