I need a grease gun to grease my riding mower. I have used a couple of different mini grease guns and it seems the piston is to small for the cartridge and grease goes past wasting much of the grease and quite honestly sometimes no grease comes out as it all goes past the piston. What am I doing wrong? Steer me to a good grease gun. I am even willing to go back to the old fashioned ones which I sadly threw out when new cars didn't have grease fittings.