I don't know if you'd "kill yourself", and have never used "french polish" as a finish, but will generally guarantee that if you don't use some form of grain filler/sanding sealer on swamp ash the finish will "sink" down into the grain pattern and you'll get some dimpling/"orange peel" on the smooth parts in between the grain as it dries.
French Polish will work as a grain filler when it us used with pumas and rotten stone. That is how they do the high end classical guitars and one reason they cost so much. It is very labor intensive. You can find a good amount of information regarding French Polishing on the internet. I think the Tru-Oil may be an option for you and there is a lot of good people on the board that would help you with it. If you choose French Polish post pictures of the process so we can see how it goes.
that is an awesome job! i'm a little confused though. you said you used tru-oil and the french polishing method. does that mean you didn't use shelac? whatever you did looks great, please give us a bit more explanation as to what and how you did it.
French polishing relies alot on the right amount of friction to sort of "vaporize" or melt the shellac. It is possible to use this method with other materials.
1. Take a cloth and fold it in from the corners and make a "wad" of cloth. Use a rubber band to secure the wad. It will look a little like a comet if you do it right. It will have a "tail" which you will hold onto.
2. Put some finish on the piece of wood. You will want to let it sit just a little but not get tacky.
3. Put some finish on the wad of cloth. The part of the cloth you working with should be smooth.
4. Going with the grain move your hand back and forth. Your motion should create an arc that just touches the wood at the bottom of the arc. Work back and forth across the wood.
5. The key is to hit it with just the right pressure and keep your cloth just damp enough. This will leave a light smooth coat. There should be very little need for sanding in between.
It takes a little practice but once you get the hang of it, it will go quickly. You can practice on any piece of wood and Tru-Oil is inexpensive. Also the more coats you get on the easier it is to build a shine. I put a board to hold the body where the neck would go. I put the board across my lap and the body hung off to the side. That gave me plenty of control and made it easy to see what parts of the body were getting the finish.
BTW... both those pics are 5 coats each. For the cloth I used a clean old cotton t-shirt. That cuts down on lint and is nice and soft.
I also use the French Polishing method with Tru Oil for my neck finishes, and believe this is the finish for a great playing Maple bass neck. I have also finished an Alder body with this method ... but I thought the finish was a little thin, and that the wood took a little too much punishment.
There's a bad ass Black Korina Jazz Bass that's been in the Showcase for a while, have a buddy that wants me to build him a bass, we'll see if that's still there whenever he finally comes up with the cash, would look great with that canary/ebony Jbass neck also in the Showcase: