Forgive my ignorance, for I have generally used mnemotechnics for non-competitive (learning) uses.
How did you mentathletes out there learn your system?
Did you decide on images for each number first then ram them in using Anki/flashcards? Or was it a gradual process?
Does your card/binary system use the same images as your number system?
Do you use a different system for each discipline (e.g. Category for cards, Major for numbers)?
Did you start out at two digits then move up to 3, or did you just go straight to 3 digits/2 cards?
Did you find it difficult to change system once you had learned another system? Do you get interference from the first system?