I am still trying to learn her cues but here is what I found so far- when she is in my arms feeding and starts kicking or going straight legged, looks like she wants to feed but keeps popping off, or gets super clingy and won't let me put her down, she usually has to go. Just be consistent with your sign and when you are offering potty (I do into/out of highchair/car, before/after sleep/naps, right after or shortly after a feed). It might take some time for them to sign back and out may not look exactly like how or should at first but don't very discouraged. I also try not to force the potty if they aren't having it or get discouraged when we have more misses than normal (apparently they can go through potty regressions just like sleep regressions🤷). Good luck!
I am definitely not an expert (I started a little after 6mo and my LO is now almost 10mo- also just wanted to say that you are definitely not late 🙂). I part-time EC and started with easy wins. I incorporated the poop sign and a noise prior to strating EC but not because I wanted to start. I breast feed and noticed she would always poop within 10 minutes of waking from sleep/naps-so I just sat her on her little potty and did the sign/sound. I let her feed while sitting on the potty (I think the leaning forward to suck helped push it out) and when she finally started, it made a big noise that startled her a bit but I just praised her and made the sign/sound again. Then just started increasing potty opportunities and giving her lots of diaper free time(so I could try to learn her cues). She still doesn't sign for pee/potty but sometimes she makes what looks like the poop sign.
Signaling can take a lot of time and development. If you can do observation time and diaper free time to understand any subtle queues (@Cynthia) mentions some great ones, and doing transition times, that will build over time. We found queues changed all over again at each big development stage. And know you’re not late to the game! You’ve started at a great time!