Have you ever suffered a clear coat disaster?

Several,

1) Applied too much clear coat too early which basically melted the paint underneath. Lesson learned: Wait longer until the paint is completely dry. Apply lighter misting coats if not going for a glossy finish. 

2) Used the wrong kind of thinner and not heavy enough coating which cause the finish to look like sandpaper. Lesson learned: Use leveling laquer thinner or actual thinner with paint retarder and not IPA for a smooth finish. Apply heavier coat for for a glossy shine.

3) Used Pledge (Future) for clear coat before decalling. Lesson learnd: Testor's glosscoat works much better, is much more durable, more forgiving, dries faster, looks way better, and performs flawlessly for decalling and weathering. Will not use Pledge/Future for cloar coats ever again.

 4) Not priming my model cause paint peel and noticable flaws in the finish. Lesson learned: Priming is essential for a stable base coat and to work out flaws in the finish before the final coat.

I love testors dullcoat - learned that once I'm done shaking it up, shake it up for another 5 minutes.  Last time I coated my spitfire I got little white flecks attributed to (by other folks on the forum) improperly mixed/shaken.  I was able to knock most of it down with light sanding

Humidity.

I found Humbrol Clear gloss some years ago and just love it, water based self levelling varnish that can be brushed or sprayed (I brush with great results) but one day the finish went cloudy, Google tells me this can happen with varnish and high humidity, it was a rainy summer day here on the north coast NSW Australia so that answered that and to fix it was easy, when not  humid which the ac fixed I just recoated and the cloudy haze was gone.

Not the end of the story, I love the Clear gloss still and was very happy when they released Clear matt but no matter what conditions and how much shaking and stirring you do it clouds over. Tried contacting Humbrol, no answer and ended up throwing the bottle. Couple of years later I thought they must of fixed it by now and bought another bottle, nope, not as bad I must say from memory but any clouding at all is bad of course.

Still use and love the gloss but use Humbrol Matt cote to seal it all up. Have a bottle of Testors dullcote here that I have never tried so must give it a go.

Mick.

Nope....

I only use Testor's MM Gloss and dullcote. I "Discovered " that if you use a damp paper towel to clean your model before Dullcoating, make sure the model is dry before spraying the Dullcoat. I wound up with little white spot's all over.

This did give me an idea. I "duplicated" my mistake on a heavily weatherd box car. It looked "Just like" bird poop, from a flock of Pidgen's ( Which was "EXACTLY" what I wanted !)

The biggest problem I have had with Glosscoat is not getting all the dust off model first.  Glosscoat sure shows up any residual dust!

I've found and still having problems with "more is not always better" especially with the testors dull and glosscoats in rattlecans.  I've had massive pools of hardened laquer and had problems with spots.  I've learned that IPO will remove the laquer but it's messy and it will remove decals.  For the irregular spotting issues I've found spraying an acrylic clear coat will even out the finish.  

My go-to clearcoat - gloss, semi gloss or flat is Rustoleum brand.

Yup... first time that I used Micro Scale clear flat... it came out horribly leaving a milky appearance and white tide marks when dry. I don’t remember how I removed it exactly. I think mostly with some ultra fine abrasive of some sort. 

What I learned was never to use that stuff again. That was the only modeling product that I’ve ever thrown away without using it all up first. Their gloss coat works just fine though.