How can I cause (yes, cause, not prevent) bloom in chocolate?
Sugar bloom is a bit more stable than fat bloom, so if you like that effect I'd suggest that you try to leave the chocolate first in a slightly warm and damp environment, the sort of temperature that would make it really soft, and once it is "sweating" move it to a freezer.

Sugar bloom is caused when the moisture from the chocolate gets slight separated from the chocolate, it dissolves the surface sugars and then evaporates, leaving sugar crystals behind. So it might be possible that spraying a soft warm mist of water might help accelerate it.

I never tried to have sugar bloom intentionally, but I'll give this mist technique a shot and let you know.