WGB, Howdy;

Reamers are good but might I suggest a Hone, something like this;
https://www.aliexpress.com/item/Winm...307870274.html
The stones will polish the inside of the tube and take of the minimum
amount of materiac at the same time. A reamer will remove material
and can clean the interior it just eats more material faster.
Go down to your local Autozone and ask to see their Brake cyl. hone
the spring loaded legs will allow you to insert it into the tube and as
it cleans up the corrosion you'll see the interior start to shine.

hank