Have you heard about the Mobile Poultry Processing Unit? I know Mockingbird Farm in Easthampton, MA uses it to slaughter their birds. I don't know if they would do your birds, but definitely you can go help them with their birds and they'll teach you how it is done. Google Mockingbird farm and give them a call, his name is Pete and he is lovely. He can surely help you find what you need whether it be someone to do it for you or to find a way to do it yourself.
This is from an older thread but you can try them.
Den Beston's Farm
8 North Street
Route 104
Bridgewater, Mass
1- 508-697-6500
They do poultry on Saturdays as a walk in first come first serve basis and on Thursdays by appointment.
The rest of the week they do other types of livestock.
I know this thread is old, though I came upon it....
I was looking for a company in either MA or RI
The company listed below has bird drop off 3 days during the week I think the days were M-W-TH drop before 8m pick up same day as drop off after 3pm
$3.00 a bird they put on ice and box... Additional cost if you want them bagged a special way.
The lady on the phone was very helpful and super nice! I'll report back once I have my birds done.
Baffoni's Poultry Farm
324 Greenville Ave Johnston, Rhode Island 02919 (401) 231-6315
Thank you for the info unfortunately I got a cockerel with my all "female birds" order...so frustrating trying to find a solution to the error. He is a beautiful bird and if it were up to me I'd keep him but the neighborhood has a no rooster ordinance. Stupid I know. He is 7 weeks old as of april 21st and a lovely New Hampshire Red cockerel. If anyone wants or needs a roo I live in Charlestown RI and would happily meet someone halfway. I'd hate that he had to be slaughtered but if I can't place him then I have no choice. Too bad that vet's haven't figured out how to neuter a cockerel, lol.