So the beat way to tame a giga would be to use the grapple hook. It allows you to hang over the giga and keep his attention on you and not other dinos around you. You want to either use a quetz or argy and have a buddy fly it. Also once the giga is down allow his torpor to drop to the last bit and pump him full of narcotics using the amount the app specifies. It will save you a lot of trouble and you can literally go do anything else for a solid hour.
I dare you to raise one!! They are savage if you got two high lvl parents (about lvl 140ish) and you get imprinting on it. The thing will become an adult with about 230% melee and basically one chomp any bronto!!! But on the down side you loose your job and your girlfriend