After spending a few months with my tumbler and using corn cobb media, I find the job of digging the corn cob media out of Phillips screw cross-hairs and straight-slot screw slots that were getting clogged up to be a general PIA.
I tried leaving my tumbler empty and then tossed all the screws back in and tumbled them for a couple of minutes to see if this would help avoid a PIA job.
It is not 100% but it did a good job cleaning the media from most of the screw heads.
Your mileage may differ, but it is worth you giving it a try.