If you are still tracking your thread, I've got some information for you. First congratz on inheriting your fathers Winchesters. Next, you are probably already aware that model 12's are very popular and collectible. Prices range from a low of 250 to a high of 4k depending on the model and condition. I restore firearms for a living so I'd like to put to rest the mistaken notion that restoring a firearm severely devalues it. That simply is not true. When done correctly, restoration can, in fact, increase it's value. The key word being "correctly". Anyone can take a piece of sandpaper and attack rust and pitting on a firearm. I see this kind of shade tree work come into my shop all the time and it makes me shiver every single time.
Removing rust and pitting is not that difficult if you apply the proper techniques and take your time and pay attention to what you are doing. Rust removal can be accomplished many different ways using chemicals such as Naval Jelly, hand sanding, and media blasting. It is more difficult to remove pitting but not impossible. Most of the time it's done by hand sanding but another technique is draw filing. Most often this technique is used on flat surfaces but it can also be used on rounded surfaces if you pay attention to what you are doing.
Once the rust and pitting have been addressed, the next thing is applying the new finish. Finish options are varied but to do things correctly, you need to apply a finish as close to original as possible. In the case of your model 12's (aside from the trench model) that would be a blued finish. In the end it is totally up to you how far you want to go restoring your shotguns. Almost all of my customers bring firearms to me that they have inherited from other family members and really have no problem paying the price to bring them back to their former glory.
You are partially mistaken when you mention that bead blasting will remove pitting. Media blasting does remove the surface finish but unless you are using a highly aggressive material, you will not get below the pits. That must be done by hand. Also, patina is any finish that you have on your firearm including surface rust. It's all just oxidation over time. But most often it is not the type of rust you can knock off.
GCA and RSA Member, NRA Life Member