I've only ever matched stain by trial and error. You will need to a piece of the wood you intend to use. It must be a piece cut off or an extra piece because different wood takes stain differently. Then get a bunch of tiny cans of dark stain. Try each by themselves if no one color matches the original color then start mixing. Make sure you write down the mixture or you won't be able to duplicate it! Once you have a match get the amount of stain you need for your pieces and stain away.

To get paint drips off I use a very sharp razor blade. I've tried goof-off with limited sucess. Razor blade works better. If there is a little discoloration after the paint if off I use a little mineral spirits to buff it out.

Go to any paint store and they will have pigments to darken generic stains. Yes, it's trail and error but if you use the same type of wood you will be staining, without too much trouble, DH has matched our dark stain in our 1912 era house.

Pigments have to be mixed with the same kind of stain you are trying to apply. For example, oil based/water base.

Good luck! It's not that hard.

Most lumber stores have wood scraps to use as samples.

Also keep in mind that if you clean your existing wood, the "color" will change as the grime comes off.

They showed this in a article in the Fine Homebuilding mag I just got. They used a combo of die and stain over the top and then a varnish or shellac finish. It gave very nice results and looked just like a door with the old stained patina.

They may have something online, or maybe you could find the Mag at the library. It is the most recent issue, I got mine on Friday.

You would still have to practice to get the right color.

Cathy

My dad and granddad were serious pro woodworkers. They often did flawless repairs to some valuable antiques. I do know that matching stain is quite difficult, but they had a few cheap and easy tricks.
One being tea or different types of tea. It was mostly trial and error. Later on Dad would used instant coffee. I know what your thinking, but believe it or not it works. For new pieces,I remember finding a few cardboard canisters with powdered stain, the contents, was various pulverized insect bodies.