What is the Skill Check (Poison Kit) amount to apply the poison? Not the Save Roll; 10? 15? 20? 25?
DMG:
A character can instead attempt to harvest poison from a poisonous creature, such as a snake, wyvern, or
carrion crawler. The creature must be incapacitated or dead, and the harvesting requires 1d6 minutes followed
by a DC 20 Intelligence (Nature) check. (Proficiency with the poisoner's kit applies to this check if the
character doesn't have proficiency in Nature.) On a successful check, the character harvests enough poison
for a single dose. On a failed check, the character is unable to extract any poison. If the character fails the
check by 5 or more, the character is subjected to the creature's poison.
The PHB does not say the user of the Basic Poison has to make a check:
Poison, Basic. You can use the poison in this vial to coat one slashing or piercing weapon or up to three pieces of ammunition. Applying the poison takes an action. A creature hit by the poisoned weapon or ammunition must make a DC 10 Constitution saving throw or take 1d4 poison damage. Once applied, the poison retains potency for 1 minute before drying.
Poison (p. 257). The description of ingested poison has a new sentence after the first: “The dose can be delivered in food or a liquid.”
The other three poison types have new descriptions:
Contact. Contact poison can be smeared on an object and remains potent until it is touched or washed off. A creature that
touches contact poison with exposed skin suffers its effects. Inhaled. These poisons are powders or gases that take effect
when inhaled. Blowing the powder or releasing the gas subjects creatures in a 5-foot cube to its effect. The resulting cloud
dissipates immediately afterward. Holding one’s breath is ineffective against inhaled poisons, as they affect nasal membranes, tear ducts, and other parts of the body.
Injury. Injury poison can be applied to weapons, ammunition, trap components, and other objects that deal piercing or
slashing damage and remains potent until delivered through a wound or washed off. A creature that takes piercing or slashing damage from an object coated with the poison is exposed to its effects.