RE: Whats happened to Monocoat ?
I had similar opacity problems with yellow Ultracoat. It was very user-friendly when applying to a surface and going around corners, but the darker grain of the wood is visible through the yellow. Also, I purchased a "Coverite Pocket Thermometer" to get the iron to the correct temperature. 220 degrees F to apply Ultracote, and 300 - 330 degrees F to shrink as indicated in the instructions.
As for Monokote I do have one plane covered in flat Olive Drab monokote that looks great 5 years later. But I've moved on - no more monokote.
Lately I've discovered spraying flat, clear, Krylon over Ultracote and feel like a kid in a candy store. It's such a cool flat finish. Have also discovered carbon fiber Ultracote. Apparently it was very popular several years ago but is passe' now. I manage to discover cool things about 5 years too late.