Actually it doesnt matter if you hook up the positive cable last, the neg to battery or neg to block or body last. Current flow is current flow, same spark. The only difference might be to connect the negative cable at the body or block last so the spark will be further away from the battery which is outgassing or producing Hydrogen (bang). I always blow on my lead acid battery before I hook it up.......Had one blow up in my face once...Thought the battery charger was off, it wasnt. The last thing I saw was blue flames before they dragged me to the sink and dunked me. Lucky for me , no damage.