Hi,
just another thought.
As with every other patient, but especially in the area of learning difficulties, it is repetitive practice which will lead to success. Increasing confidence for walking is not an area that should be specifically targeted by a Physio, but the whole team.
I don't know how often you see the patient and for long he can actually walk, but I would suggest for him to practice walking (max. tolerated distance) in the pattern and with the aids that you have perscribed for at least 4 times per day [this is not evidence based; but practical]. Now, your job is to find ways to put this into action. Discuss it with the team like Nurses, OTs, etc. (to ensure that everyone e.g. gives only 1 hand support), use Therapy or Nurse aids, instruct family, ...
It is very difficult to challenge patients with learning difficulties. So, as said above, you use the support they feel comfortable with and then gradually reduce over time. In Physio, you could break down walking into the specific steps and then practice those single tasks by reducing the amount of support or adding other physical or vestibular tasks. E.g. patient might be able to stand independently, therefore practice catching throwing a ball, pass a flanel around body and under knees, roll a Swiss ball forwards and backwards, move a glass of water from chair to higher ground, progress to kicking, etc..

Good luck,
Fyzzio