Rich - I don’t know of any way to count and play at the same time really well. If I try and play and count out a part at the same time to a student, I almost always goof it up. It’s too much for the brain.
My tactic would be this:
Can you sing along to songs?
If you can sing along to a piece of music like “(I Can’t Get No) Satisfaction” by the Stones, I’d say you’re already an ace at syncopation. And if you tried to count it, you’d most likely trip over yourself.
Playing the bass can be as easy as singing. That’s my basic philosophy for trying to work on syncopation with folks. If you can sing it, you can play it.
Focus on making the syncopation singable and as easy to sing and think about as your most ingrained favorite song. You can even put words to it if that helps.
Anything to move it from a cerebral activity to a guts activity.
A drumming / rhythm reading class would also be awesome - something that focused only on rhythms. I had good luck with takadimi because it put voice to syncopation in a way that worked for me.
Best of luck! Please keep us informed if anything helps. You are not - by any means - alone with this difficulty!!