"Start at as low a speed as possible and not stall the tractor."
+ 1. We had issues engaging our brush hog with our MX5800--violent shaking, engine stalls, etc. Our PTO is engaged electronically, by turning on a switch. We learned that one factor was that our tractor tended to stall or sputter at idle rpms, which are about 800 rpms. Just nudging the rpms up to 1,000 made a significant difference. Where possible we also lower the mower to the ground to eliminate the mower shaking when engaged. And we replaced our too-short PTO shaft with a longer version (courtesy of Everything Attachments, from which we bought the mower). No problems now.