good glow plug tool. buy 1.craftsman 1/4 extension, no 43393 2. craftsman long 8 mm socket 34622. 3. harbor freight rare earth magnets no.67488. put socket on the extension, put 4 magnets in the socket. now you have magnets to hold the glow plug in. see it was easy.
I stick to 20% for backyard bashing, however, I'm hearing guys saying 30% is great for high performance racing purposes, but BE CAREFUL! different blends need different tuning!