For speed, accuracy, simplicity and comfort it's difficult to improve on a Makita flex wheel while setting in a comfortable chair free handing with the blade extended across my lap.
I use a Dewalt DWMT70782L air compressor tool with grinding, sanding discs. You don't want to make waves in the blades by taking off too much material using a grinder. Also you don't want to change the hardness of the blade by making too much heat (changing temper). You also want to follow the angle by the manufacturer.
