Hi Sazwaz
I work with horses and ponies every day (on a Highland Pony stud, and with my own, and do freelance work as well), and I've started a few Shetland ponies for driving.
I see your pony is a 2 yr old; what can you tell me about his temperament/attitude, your handling of him, and any training you have done with him to date?
I know the ladies at Thordale and they are very experienced with native ponies generally, and Shetlands in particular...........they would be able to supply you with 'klibber' tack, which is a type of pack saddle and is what was used traditionally to carry baskets with peats and feed in Shetland. These ladies know me as 'Aengus Og' in case you wish to mention me to them.
Shetland ponies are no different to any other horse when it comes to preperation for work, in that they have to be well handled, biddable, steady to noise/traffic/other potentially scary stimuli before they can be expected to start training for work.
Although your pony is still too young to start in work, there are still many things you can be doing to help the training process to be enjoyable and (hopefully) successful when the time comes, such as halter training, walking out in hand, feet lifting, introduction to some items of tack, and bitting (if you plan to use a bit).
Provided you are sensible when doing those things, your pony should be ready to start training for work as a 3 yr old, with a view to starting some light work when he is four.
Keep any lessons short and interesting, asking him to perform simple tasks, bearing in mind that he may take a wee while to understand what you require of him but, as long as he's willing to offer something, you just keep asking till he gets it right, then praise with the voice...........Shetlands are quick learners, although that applies to bad habits too.
Work out a repertoire to use when you are training him and stick to the same commands all the way through, as too many different commands can easily confuse youngsters.
If you find that things are not going so well any time, ask him to do something he's good at, and stop there for the day, then try again another time, and don't worry if things go wrong.........as long as you work safely it's all grist to the mill in terms of the end result..........like us, horses have to learn from their mistakes sometimes.
Good luck.