Referring to clear coat only: Every time I tried the "old hippy" method it cracked again, only sooner. In fact, every time I've had a surface partially painted or done it myself, it's cracked eventually. Pisses you off 6 years later or 6 months later, whenever it happens.
The cracking may be due to paint incompatibilities, differing shrinkage rates, climate (inside during painting) and/or prep. Whatever the cause, it never stops until the clear coat peels off. I'd get whoever to sand off 100% of the clear coat, top coat the paint and clear coat again.