https://thegreatmodel8.net/

This is not specifically about a Remington, but could be if your shotgun takes the Browning "Invector" style choke tubes, and many non-Browning shotguns do (I think Remington does). These tubes are flush with the end of the barrel when screwed in place.

Two weeks ago I got back my 12 ga. Browning Citori O/U back from my son who's had it over 10 years. First thing I did was to try to loosen the choke tubes - no luck with the little puny Browning wrench, as they were frozen solid in place. I understand this happens when they are left standing for a long time. Anyway, the first thing I did was to remove the barrels and stick them muzzles down into a container of penetrating oil. I tried to remove the chokes periodically since using the useless little wrench, but no luck.

Today, I decided to make up my own removal tool. It was pretty simple. I just took a small piece of 1/8" mild steel and cut an approximate 1" square. I finished it off in my milling machine, but you could use a file instead, would just take longer. On one end, I milled it exactly 0.808" wide to fit into the choke tube slots, just like a screwdriver, but again a file would work to do this. If you have another gauge, of course the width would be different than 0.808" I clamped one end of my tool into my bench vise, stuck the muzzles into the 0.808" end, and twisted the barrels. The choke tubes came loose immediately without hesitation. I love it when a plan comes together.

I think it's important to have sharp square corners on the tool to grab tightly on the choke tube slots. Another tip would be to either remove or loosen the choke tubes if you are going to put your shotgun away for an extended period.
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My mistake - Invector tubes fit Winchester, Browning, Mossberg, Weatherby & Savage shotguns, not Remington

I do re-bluing and repair and stuck choke tubes are an issue I deal with almost monthly. Soaking in Kroil and using the big "easy outs" is what I use but your idea sounds great too...d2

I have read that using "inside pipe wrenches," available in several sizes, used by plumbers to remove threaded pipe broken off at a fitting work well on stuck choke tubes. The idea is the same as an easy-out, but the design is different. I would think the use of an IPW or easy-out for removal would carry a risk of damage to the tube. Not a big deal, as I see lots of used choke tubes at gun shows for $5-$10 each. Some suggest that moderate heating of the shotgun muzzle with a heat gun or propane torch helps free stuck threads, and that was my Plan B, which proved to not be needed. My simple little metal square worked fine, and I hope I don't need it again. It's now residing in a box with a number of other one-time use tools I have fabricated over the years for gun-fixing (and other) purposes.

I thought later that I could have very easily cut the other end of my little tool to a width that would fit 20 gauge tubes, and would then have a 2-in-1 choke removal tool. Maybe I'll make that modification if I ever have a stuck 20 ga. tube.