Grandma's and forks are common.
Mine would touch it to her lips and if she had to pull it away that bird was plenty done. If she could rest it there without a thought, back in the bird went.
A trick I use on chunks of random meat (also no skin) is to start the oven high like normal then back it of 50 to 75 degrees after about 15-20 minutes. This helps the meat get a little bit sealed up then slow cooking to preserve what moisture is inside. Honestly the fat doesn't do much in my opinion, its the moisture barrier that the skin provides naturally that has the greatest impact on the meat. Another reason salting the meat or brining does such a good job with any, but double so with skinless meat.
The other really important simple trick is to let the finished product rest for at LEAST 20 minutes before you cut it. Otherwise lots of flavor and water just floats away as steam.
So many good turkeys get a poor death because they are carved immediately out of the oven.
After you get comfortable you can use the tricks together and take the bird out when its still not quite done cooking and cover it or bag it and let the last bit of cooking happen in its own juices... Yummy!
Those oven bags really cant help much except for those last few minuets and contribute to a poor quality gravy if used for the whole session.
Although if you are going to whiskey or cognac soak the bird they do help those flavors stay in because the alcohol cant escape as easily.
Ahhh
real pan dripping gravy, left in the fridge to get the fat out and then reduced...
I need a farm chicken NOW!