If you have a quetzal then you can use it to for over the giga then unmount on the platform and make sure to use the compound bow with shocking arrows. Make sire to aim for the head and hit consistently and bring At least 200 arrows. This is one of the safest and quickest ways to knockout a giga. You can then wait a while when it is unconscious make sure not to feed it. And when you have waited for a very long time and made sure not to feed it and keep it asleep and alive with membrane then use soothing balm if you have some and feed them some food. The taming bar will go up extremely fast this way and it will keep you safe.