I rely on a couple tricks that Wendy taught me
1) Spend some time looking at your cat's SS a bit every night and try to see if you pick up any recent trends. I probably look over the last 1-2 weeks. Do I see Bell bouncing after a specific low number range? Do I see rapid drops causing bounces? How many cycles does it take her to clear a bounce? What patterns do I see when she breaks the bounce (this one is most important to me since I know Bell goes lowest during those bounce breaks).
2) Treat your BG readings like a guessing game. Based on #1, see how close you can get to your meter.
I also pay attention to how Bell acts during certain numbers or situations. I use this more to know when I need to poke more frequently. If Bell cleans her plate in a frantic way, I know she's in the low greens/limes. If she finishes her food normally, she's prolly in the yellows or pinks. If she isn't super interested in eating, she's most likely in the blues on her way up or down. If she's clingy, she's low. If her eyes are watering a bit, she's bouncing.
All that being said, I'm wrong a lot