I fry turkeys for quite a few people at Thanksgiving and Christmas (I typically cook around 20 birds each holiday). Here are my tips, recommendations, etc. First, I highly recommend the Cajun Injector Creole Butter marinade, it is the only one I use and everyone loves it. Second, while most people frown on it, I use regular vegetable oil. It's cheaper, and it performs perfectly well. I will not use peanut oil, because I cook for so many people I fear that someone might have an allergic reaction. Also, while the Cajun Injector site says to never fry a turkey over 14 pounds, I always cook turkeys between 18 and 20 pounds. Actually, the Cajun Injector site contradicts itself a bit. It says to never fry a turkey over over 14 pounds, because you don't want to cook one longer than an hour. However, their cooking time (which I agree with) is 3.5 minutes per pound. So, you could cook a 17 pound turkey in 59.5 minutes, which falls below their hour boundary. As for the skin, I always sprinkle a liberal amount of Lowry's seasoned salt on the outside. It gives it a great flavor, if you like to eat the skin.
Every year, the number of turkeys I cook grows, so I assume I am doing something right. I don't make any money on them, I just do it because it's a simple process. I actually recommend getting together with other friends and cooking more than 1 at a time, for a couple of reasons. First, it's better to make one mess than two or three (oil WILL splash out of the pot, so make sure to be in a spot where this will be OK). Second, you can fry several turkeys in the same oil, so the cost per bird goes down drastically. This is a BIG benefit, as it takes a substantial amount of oil to fry a turkey. Also, if you have never fried a turkey, I HIGHLY recommend the water test method mentioned earlier in this post for determining how much oil to use. Too much oil is a very messy (and very dangerous) thing.
I hope you all enjoy your new fryers.