1. Find someone who has the card you want to measure and a large variety of other cards in the same rarity or type. If you are measuring a rare card, you want to pick someone who has a lot of rares with varying counts.
2. Open a new trade with that user and put the card you want to measure in the trade window.
3. Sort their collection by cc, pick a sample of other cards of exactly the same rarity with high and low cc and put them in the trade window along with the first card.
4. The trade window will sort the cards by awards first, then by rarity, then by CC within each rarity. So if you want to measure a non-award rare card, make sure you only pick other non-award rare cards. (My previous experiments with this mixed rarities or awards with non-awards and gave me bad data.)
5. Cards with lower cc will be on the left, cards with higher cc will be on the right. Sort the collection by CC and start narrowing down the range, taking note of if cards are placed to the left or right of the N/A card.

Example: The 2022 Oak Omnibus War Machine rare card has N/A card count. I found through trial and error that the cc of this card is either 2919 or 2920. A Topps Now rare card with cc of 2919 sits to the left of War Machine in the trade window, and a Topps Now rare with 2920 sits to the right.

Topps_David actually messaged me in a trade window in the app and told me that my previous post was incorrect. I'm hoping that I found the flaw in my logic. Thank you to the user in this forum who pointed out the flaw - mixing rarities and awards.