Hands-on, as you did with the marshmallow counting, is what I'd recommend. Anything they can manipulate and move around has worked well for my probably-VSL kids. My kids actually like using paper and pencil a lot, too, so don't rule that out. Seeing it on paper or in a book can work for some visual learners.
But be patient. Since it comes as an "aha" to these kids a lot of the time, they aren't always the ones who are way ahead in achievement at these young ages, but they can jump way ahead all of a sudden. Fits and starts seems to be pretty common.
I hope you get more help than mine. I'm reading with great interest!
