First off, the adhesive on the back of the monokote is still ok ,dont use rubber cement etc! Secondly, if you've heated it up a few times with the gun and the wrinkles are returning, it's time to take out the iron. If you don't have the coverite version, I recommend it. Use a sock over the iron. Set the temp a little over 300 with the coverite thermometer. There is an art to getting the wrinkles out, you cant just smash them down. Heat up the covering adjacent to the wrinkles first, and then move the iron away from the wrinkle to push the excess covering away and redistribute it. The last place to iron is the wrinkled area. If there is a bubble, now is the time to stick it with a standard pin, not a medical needle, then gradually heat around the area, moving the iron and the trapped are towards the pinhole.

Sometimes I get the covering too hot and it puckers or wrinkles up. I find if I wait a week, the covering relaxes and I can go over the area again with the temp down a bit and smooth it out.

The key is to understand that you can shift the covering around a bit with the iron and then adhere the covering to the wood so the wrinkles wont return

Peter