One way to tame Kirix is to first make certain you are using [Aspect of the Wild]. When you pull him, he will use a knockback ability - use your [Disengage] at the height of this. [Deterrence] when you land + [Tame Beast]. Anything that adds to haste will be useful here, as the lower your health pool is, the higher likelihood the tame will fail.
Another method is to employ the floating rocks in the area to tame from. You will still be hit by his special poison attack.
For those wanting the skin but not the challenge, some Cinderweb Broodlings reportedly spawn within the Widow's Clutch[65, 42]. There are two types: one kind that spawns from the Scout's body (not tamable) and another kind that quickly move through the area. The latter are rare to find.