You might want to get some Hibiclens (chlorhexidene) or Betadine (Equate First Aid Antiseptic) at your Walmart or pharmacy. Vetericyn is good for wounds, but the latter 2 are used in hospitals to disinfect wounds. I would irrigate the wound with a large syringe or turkey baster.
As for antibiotics, Baytril is very good, and can be obtained online. It is banned for chickens, but some vets will prescribe it for serious infections or wounds. Eggs should not be eaten for at least 5 days, and some even wait up to a month after stopping it. The dosage of 10% Baytril is 0.05 ml per pound or 0.25 ml (1/4 ml) for a 5 pound chicken. A small 1 ml syringe without a needle is available at most paharmacies free for giving infants medications, and good for small dosages. Here is where to find Baytril:
https://www.jedds.com/shop/enro/
As for antibiotics, Baytril is very good, and can be obtained online. It is banned for chickens, but some vets will prescribe it for serious infections or wounds. Eggs should not be eaten for at least 5 days, and some even wait up to a month after stopping it. The dosage of 10% Baytril is 0.05 ml per pound or 0.25 ml (1/4 ml) for a 5 pound chicken. A small 1 ml syringe without a needle is available at most paharmacies free for giving infants medications, and good for small dosages. Here is where to find Baytril:
https://www.jedds.com/shop/enro/

I think that you are doing well in cleaning that wound, but I agree with Eggsessive that a better antiseptic would help more for irrigation. You can get chlorhexadine (Hibiclens or Nolvassan are two brand names) from most feed stores, or betadine from a pharmacy. For either, I’d dilute to about 1:30 with water. For betadine, that should be the color of weak tea. For chlorhexadine, that will be a pale sky blue. I think Epsom salt solution may be best for that vent. It looks like there may be more tissue that needs to removed. Any dead/non bleeding tissue is a place for bacteria to multiply. She will slough some herself, so you don’t need to get every bit, but anything loose should be removed.