Timeline:
Now: grant application
Soon: GG21
After: funds released

10 days: research about the platform where to run the competition. Generic design (99 designs) or something dedicated to psychedelic art.
1 month: reaching out to artists (most likely on Instagram) to let them know about the event
(in parallel): reaching out to jurors who will evaluate the work and engaging them in marketing efforts
10 days: judging and announcement 

Budget: split between the prize for the artists and operational effort (opportunity cost of time running the competition)