1:41 PM: today when i awoke i knew i had to bite the bullet and contact apple support to receive guidance on how the almost 500GB of i-Movie projects on my iMac desktop could be safely moved to an external drive to free up space on my 1000GB internal hard drive, which has been reduced to 17.5GB!
so far it's been far easier than i had feared it might be. right now 1 350GB folder is being exported to my seagate 5TB external drive. then apple support will call back at 3:30 to guide me through the rest of the process and finally trash the 500GB on my internal drive to free up the space. from now on, all i-Movie imports of media will go directly to my external drive.
more info than you wanted, i know. this by way of saying that, so far i haven't done any painting. but i'm about to stretch the canvases & will likely start a new painting: grey 24, either later today or in the morning.