Manual methods have been common in the special education aimed at (talking or non-talking) cognitively disabled and/or autistic children. Using cards we have taught reading and writing skills, basic maths, signs, locig and PECS -like comunication, too.
Cards and materials are hard to produce. They are even slower and clumpsier to administer in daily life, not to mention the problem of proper storage. Concentration gets lost and we do have time and possibility for very few repetitions and variations. THus, we tend to cement kids on a level far from their own potential.
Our method, putting signs and symbols into Lexion (that exists as Lexion in English), enhanced the productivity of special education 40-80-250-fold (not %) per month, ie. 2,000-fold per annum. The results are stunning after a regular one-hour-a-day use. We could easily be able to offer AAC-kids materials for all their school years and subjects – in their own first language/mother tongue.
The article is in Swedish and it contains lots of illustrations.