Tarnishing new doors to match existing doors

I'd be tempted to strip the doors with sandpaper/paint stripper and then start afresh. If you want the grain of the wood to stand out a bit, rub in the direction of the grain with either wire wool or a wire brush. Clean off the dust and repaint/stain/other from there.

Depending on coulor of existing doors sand down doors and prep accordingly also flat sand them for smooth finish also varnish same coulor them after 24 hours use a clear varnish

Call in a French Polisher!!!

If you try to match finishes on the doors it will be extremely difficult, personally strip all doors and start afresh then you know you will have the same colour throughout slightly longer time but worth if you want unity.

There are a few considerations to take into account. Anyone with breathing difficulties,for dust and preparations. That as a guide you have a few choices. It’s possible to have the doors matching in time scale reverence if you know your products and what your doing. How you go about it depends on ability to use processes and products. Either way matching if you take the door back to bare wood or not is achievable. No problem. Be flexible in your approach and choices. Giving the customer the opportunity to call you in again and recommend you to friends. I’ve already matched doors one hundred and twenty years old and stair case. I have an instinct and eye for clout and tone

Yes the procedure is correct, But paint or varnish strippers work best on oil based products. Sandpaper, Dust and wipe down with white spirits..