I just butchered 8 laying hens and I would like to can them. I've never done it before and have a few questions.

We can a lot of rabbit.
Parboil for a couple hrs, pick off meat, pack in jars, strain and fill will broth, then process.

Holds up very well, and can't really tell it from fresh

I agree with Waldo.  Why cook it twice.

Raw pack can it.

I can hundreds of pounds of chicken every year.
I buy whole chickens when they are priced at .39 cents or cheaper per pound.
I throw a couple chickens in a stock pot with enough water to cover.  I cook them until they are half way cooked.
Clean the sink until you could eat off it.
Pull chickens out of pot and put them in sink to cool just enough where you can debone them. Can the chicken meat 15 lbs pressure for 90 minutes.
Throw bones back in stock pot along with any vegetables you have saved.  Bring to a slow boil.
Strain the stock pot and can the Chichen stock 10 lbs pressure for 20 minutes.
Don't over cook the chicken in the stock pot and it won't be over cooked in pressure cooker.
This method boils out the fat so the chichen fat doesn't get boiled out in the canner.

I get a better yield if I cook the chicken and then de-bone it and can just the meat.  I've tried raw pack bone in and boned and the best yield is when I cook it and de-bone it.

YMMV