I have seen a few mentions of putting clear coat over Rustoleum, but did not read about anybody trying it until I searched. This guy used Rustoleum paint and Rustoleum clear coat, but the paint wrinkled when he used the clear coat. People kept saying not to use their clear coat and someone said it contains acetone, which is the problem:
Clear coat hell
This guy did a two-tone paint job and the second color was ruined when he applied the clear coat, but the first was fine. Someone commented that you either need to use the clear coat while the paint is still wet or wait a week for all of the solvents to evaporate;
Rustoleum clear ate my base coat
Curiously, while people say Rustoleum comes off too easily, that does not necessarily apply when someone tries to sand it down to repaint.
Perhaps you get what you pay for?