I picked up a 4 foot Walco bush hog on the weekend and was going to change the gearbox lube and grease it and sharpen it before I put it to work. Here are the novice questions: what is the easiest way to sharpen it, while it is on the tractor or otherwise, and is it likely to have a drain plug on the gearbox and would it likely take 80 or 90 wt lube? Thanks.