Problem with Clear coat

Laquer can be a real pain in the ass to work with. sometimes laquer paints are the two part kind and need a sealer before you can do anything with them. other times you may need to let them dry and "gas out" for long periods of time (upwards of a week in some cases). i had the problem on an F1 car. i spent $30 on the color (in laquer), painted it and tried to clear coat it. the coat reacted with the paint and dissolved the paint, ruined the decals, and overall made the project not worthwhile to even attempt to salvage. the can said a "coat of (the brand escapes me) seal coat is recommended before decaling, detailing, or finishing". it does pay to read the fine print. i would either check the bottle or can and see if it is recommended to use a sealer or contact the company.

-The Wild Child

The laquer thinner is a LOT stronger than regular enamel thinner.  I discovered just how much so when I mixed it with Squadron White putty to make a "slurry" that someone recommended and it severely softened the stryrene.

Whatever clear coat you use, you want to use a few light coats instead of trying to get it done in one.  It's a given that it will soften the paint, which comes in handy for evening out any brushstrokes and such, but too much will cause the exact problem you describe.

You also want to let each coat thoroughly dry and cure, I'd recommend at least overnight.  Adding a second coat too soon will cause tiny cracks to appear in the finish all over.