Im a violin maker -- and that is always a thing you try to do there too. There are some drawbacks to some of the finished mentioned. Tru-oil works nice --- but it
is extremely glossy--- to the point of being gaudy. It does work good and is very easy. Tongue oil is nice to look at but even after well dry-- is hydroscopic.
It wont dry if applied in high humidity. Has to be overcoated with something else to protect it it from moisture.
Here is a general approach--- sand old finish off down to bare wood. sand from coarse up to about 600 grit. Blow dust off with air. Mix up some sugar
free jello --- about a 1/2 teaspoon in 1/2 a cup warm water. Brush on a light to medium coat onto bare wood. let dry 24 hrs. lightly sand again with 600.
Next make a stain. This stain can be made of many different things. You can make a concentrated solution of common tea. 4 small bags in 1/2 cup got water.
you can also use coffee. I have seen that work really good but havnt tried it yet. paint this solution on . You can do several coats-- letting it dry between coats.
(the jello prevents over penetration and blotchyness from differential penetration)
(dont use any steel wool untill the wood has been filled with the jello) (steel wool on bare wood breaks off steel splinters into the grain of the wood----
if you stain with tea or coffee OVER the splinters-- the tannic acid make a black dot everywhere there is a splinter--- ask me how I know !!! )
After you have stained---- you can lightly sand with 600 again to adjust the opacity / color of the water based stain. Reapply as needed until
you like the look. Once you like how it looks- find a ROUGH rag out of burlap or maybe terrycloth. The rougher the better. even an old red shop rag.....
Carefully dampen- evenly- (NOT wet) the rag with linseed oil. (boiled type) Take the rag and rub the wood really hard- trying to apply a LOT of pressure-
you are trying to burnish the surface and generate a little heat...... Keep doing this until you see the grain pop out. you can burnish right after the jello fill-
but the oil kind of seals off the wood from any further water based things.... (colorings)
Burnish as long and heavy as you like. After thats done- let it dry a couple of days. Then you can come back and paint on a brushed coat of linseed oil.
you can tint the oil with organic dyes. The tint is not a large effect because the oil film is thin. but you can see it. Linseed makes a very tough practical and
natural looking surface. You can leave it that way for a "soft" , natural look. For a shineyer look- let the oil dry for about 5 days or a week until its 100 hard-
then over coat with gloss polyurethane or the Tru-Oil. When you paint on the linseed- you have to go THIN if its not soaking in. let it stand for an hour or 2 and come back and wipe it off with a dry rag. let THAT dry for a couple days. Then overcoat with whatever.
Try this process on several test scraps---figure out the colors and concentrations you like before you do the real piece.
maybe this is too much info ?

sorry --- I have a thing for beautiful wood......
Tim
PPS - here is what that looks like when you do it right ! This is one by Louis Manfeo- he makes one of the most beautiful
finishes I have seen. Id be happy to do 1/2 that good !