I have heard of a lot of people having success with hands on approaches to math for children with dyscalculia - math manipulatives like cuisenaire rods, pattern blocks etc.
I have no BTDT experiences, but my son attends a Japanese Soroban Abacus Math class and I have met 2 families there who had kids with dyscalculia and difficulty with counting at age 8 and 9 and they said that learning the Soroban method as well as the anzan mental method of mental math helped them overcome their dyscalculia. BTW/ there are a lot of apps that simulate the soroban abacus.
