12 lbs. is the perfect size to fry. Usually it takes about 3 minutes per pound at 350 degrees. I just buy one of the injectable store-bought butter marinades (I know, I know...) because is easier tham processing your own ingredients enough to fit through a plastic needle. I also use a dry rub on the outside (paprika, black pepper, garlic, celery salt, sage) for several hours before injecting and frying. Good luck!
Use peanut oil to fry them in. Temp and time info above is correct...when the turkey is done, it will float. The only thing I have ever used to inject the birds with is Louisiana Hot Sauce.
Don't rely on the turkey floating. Make sure that you have a meat thermometer. An infrared thermometer comes in handy for measuring the oil temperature.
We always inject them with italian dressing the day before and let them sit in the refridgerator. Let them come closer to room temp before frying.
The only thing is you need a bigger needle syringe (spelling) so that the bigger bits can go thru. Always had rave reviews. We fried 12 of them for my graduation party. Nothing was left but bones!!!