Squirt vinegar in your own face and see how you like it. If the snake bites, just deal with it. Get a snake hook. Please don't stress it into submission. Reptiles sometimes bite, if folks can't handle it then get a puppy. Our 5 ft Boas has hit me a few times. I refuse to squirt **** in her face or hold her to death. I just find a way to deal with her how she is. Just my opinion.
In guess working with hot snakes has had an influence on how I deal with non-venomous that bite. Like our texas ratsnake. He hates everyone equally.

"Squirt vinegar in your own face and see how you like it"
Actualy, if theres boardwalk fries involved, you could totally squirt me in the face with vinegar, boardwalk fries and vinegar, yummmm.
But no, seriously While I personally don't use vinegar on any of my animals, there's a very good chance these snakes will be bought by someone with even less snake experience then I have, and id rather it be a behavior they outgrew now then later, squirting them in the mouth with vinegar is not something I relish doing, but the fact is its essentialy behavior modification, without hurting them your letting them know that its not okay to continue biting. Theres still people that squirt cats with water for jumping on tables, its about as discomforting.
For the time being i've been just handling him with my pigskin leather gloves on, he's figured out when the gloves are on he's not gonna achieve anything biting, that or maybe they deaden enough of the heat, but either way he does not really go after my hands when im wearing them that often.
"I refuse to ... hold her to death"
When I hold snakes im pretty careful not to squeeze too hard...
They are benefiting a bit from the extra handling, whenever im in I make it a point to give him a little bit of extra attention, he's calmed down a little bit, but not quite to the point of letting me handle him without the gloves.
The two boas are also seperated now, in there own tank, which makes it alot easier to get them in and out, and I think will prove beneficial to calming them down a bit. Tommorows feeding day, so I'll see how they do, and if there getting enough food.

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"Nobody can do Everything, but Everybody can do Something."

So I fed all four boas today, all four of them had no problem eating a prekilled adult mouse, which was great, the ball pythons however, were fed live by one of the other employees there, and I was unable to get them to eat prekilled, but more about that elsewhere, as for the boas, We found the missing Redtail, so back to two redtails, and two common boas. After they ate today I took some time to see how the snake I had "listed" as the more aggresive of the two, the larger common boa, would do with handling, he did so well with the gloves that I actualy took them off and walked him around the store in my bare hands, this is the same boa that about a week and a half ago would attack your hand when you went anywhere into his cage let alone picked him up. between eating a full meal, being in his own cage, and all the handling and attention he's gotten he has calmed down rather fast, while I dont think either of us are ready for the face test (ill hold some smaller snakes up within striking distance of my face, see how they react, probaly a stupid idea, but im the one it'll hurt not them, and ive seen snakes that were completely fine with hands, strike at any face within reach, (both the red tails are fine with this, and dont strike or even tense.)) im actualy suprised how well he did with all of it. So next up is the smaller common boa, which I have learned, is quite a hisser, does'nt bite as much, but will make a bigger deal about coming out of his cage.

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"Nobody can do Everything, but Everybody can do Something."

It sounds like you are making progress:-) The future owners will be thankful that you took the time to work with their pets as babies.

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Kat