It’s an old technique outlined in Scarne on Gambling.

Ps. Nicholas I was wondering if you wanted a hand collating the encyclopaedia of scams. Because I have a few to add to the wiki if your interested.

So a simple guess, Jake. As to how, ordered the daub online on his iPhone after reading about it in Erdnase (I think a cheat is a cheat, reading Erdnase will teach about daub so why wouldn’t the owner use it), then used the pic of his kids to get it on his finger.

I don’t care if I’m right, I just want to stop thinking about this

You see Jake wasn’t the innocent he claimed to be. Sure, he played only with his buddies before - but that was in prison. He had smeared daub on his shaven head, and then hidden it under a wig; a scratch of the head is all he needed to get a dab on his finger. On his head - that’s where you will find the evidence.

But he wasn’t the only person there with a record. The Colonel also came from the wrong side of the tracks, and had adopteda similar approach to cards. He was *also* trying to cheat, with the same cheap daub, which he cunningly used to wax his moustache, where it was only a nose-rub away - that’s where you will find the evidence.

It was, of course, a night of coincidences! Jimmy The Rat was also cheating - he hid his daub in the peanut shells - look on the floor - that’s where you will find the evidence.

You can see where this is going, next, of course. Natasha, the buxom “Russian” from New Jersey - it is pretty clear where she was hiding her daub! In a tiny dish blu-tacked to the underside of the table. She’d adjust her assets with one hand, and reach for the daub with the other, while the men were misdirected.

Despite their best efforts at cheating, that’s not where the majority of the daub on the cards came from. Each of them had only just started discreetly marking different cards, with practised hands, but getting confused by the conflicting signals. The clumsy smear of daub over most of the cards - especially the cards that were revealed by the bar-tender - was mainly coming from the container of daub sitting in the pocket of… the bar-tender - that’s where you will find the evidence.

It seems that guy was just moonlighting as a bar-tender. His main gig was running an online cheating web-site. He noticed a cluster of customers in an area of New York - customers that ignored his recommendations to purchase a more expensive daub that he was proudly hand-making, and instead went with the cheapest daub available. He arranged to have them play together, and deliberately corrupted their markings, just to teach them a lesson about paying that little extra to get quality.

Quite a remarkable story, and if I hadn’t learnt all of it from the bar-tender one night, I never would have guessed any of it from the clues provided here.

[Drats, I wrote this before I read the previous comments.]

The colonel has a rubberband and may have flicked the evidence away with it. — the other option is his moustache

The condom packets were airtight?

My absurd answer is that they were colluding: the colonol hid the daub in his dr pepper, where he passed it via the wet towel to jake who smeared some onto the photo of the kids (could have been disguised on the glossy side), who stuck it to the bottom of the table with jimmy’s gum and natasha applied it to the card. Obviously this is very Alice in Wonderland! Haha.