Unpod a giga, it will hold agro and tank all damage until you drop its health low enough to mount. Easiest method. Staying mounted can be a pain due to lag or render (when you get to close to walls). If you get dismounted use tek punch to dodge attacks and make your way back to giga and Mount the giga it will retain agro again and get you another chance at it.

More Voidwyrm Taming & KO Tips