When I ball the ends of 18 gauge or heavier wire, I use a larger torch. The larger flame makes it easier to ball the ends of the wire. I purchased a Eurotool Handy Flame torch head when they were first introduced because it fits on a Coleman butane fuel can, which fits comfortably in my hand. Also, the fuel was readily available at one of our local hardware stores.
Product ID: SOL-315.00 - One-touch ignition multi-purpose butane torch head attaches directly to fuel canister so you can start working immediately. Adjustable flame control up to 2,375 degrees F. Lightweight, compact design attaches easily to a butane canister with a simple push and twist motion. Uses 8 ounce butane canister (not included).