What is the attack roll to lick someone?

[CattyNebulart]

At a guess i would say karate or brawling but what modifiers if any escape me. First though some background;

There is this template for a species whose tongue is worth about 30 points.

Description;
They are able to stretch the tongue between 30 and 50 cm (foot to foot and a half) out of their mouth and it's fully prehensile. In addition their tongue is highly toxic, much like some frog poisons. Flesh affected by the poison has a tendency to melt and it otherwise acts as a strong barbiturate that is highly pleasurable and incapacitating. Luckily it gets neutralized after a few minutes of contact with the air even if it doesn't get metabolized.

One of the design goals is to make licking your blade into a tactically sound decision. The precise time to neutralize the poison by air is deliberately left vague and up to GM fiat, but long enough that it would never be an issue in a combat encounter. As a blade poison it works for one strike and is thereafter mostly harmless.

Translated into GURPS:
Extra Arm (Extra-Flexible, Short, 1/4 ST)
And two alternate 3d Toxic Innate Attacks
Modifier Set 1; Side Effect (Euporia), +150%; Reach C, no parry, -35%; Always On, -10%; Sense Based: must touch with tongue, -20%; No Signature, +20%; Contact Agent, -30%.

Modifier Set 2; Toxic, Blood agent, -40%; Resistible, HT-5, -5%; Follow-up: Anything Licked recently (Cosmic), +50%.


This leads to the obvious question of how does this actually work in combat, specifically the first version which requires one to lick exposed skin. this is aimed at a DF style game but I'm genuinely curious how it would work even in more complex games.

Touching bare skin while grappling should be easy, unless the opponent is in full-plate or something so what are the modifiers and how does armor affect it?
As written I don't think the tongue could be used with striking arts (karate, brawling, etc) but all other natural weapons I can thing of use one of those, would this be a wrestling type attack? what about Judo or sumo wrestling?