I de-stem by hand but, this year a second hand kitchen mixer with a food grinder attachment is what is grinding the grapes and boy does it do the job.
Just finished this morning using it for three 5 gal batches, 75 pounds. Hope it works out on the other end.
Do it the old fashion way. Go to a dollar store, get a big bucket that you can stand in. Take it home, fill with grapes, clean feet, crush the grapes with feet and use that.