Hi Karen - you can use a two wheeled shopping trolley, if you can get one with big enough wheels but it does mean that you are pulling it behind you with one hand, which is tiring to say the least! - so a two wheeled trailer is the way to go! (whatever you do don't buy a mono wheel trailer (single wheel) as it is an awful design that leaves 50% of the weight on your hips).
You load a two wheel trailer so that the main weight is over the axle and this then gives you just a pound or so on your hip belt (needed to stop it pitching up and down).
As they are connected to a padded hip belt, if you have stability issues you can still use poles.
Hipstar have delayed actually selling their trailers for years and years but now they are going out to customers, they are quite cheap for what they are but if you go down that route get a FIRM delivery date before you go ahead.
The Radical Wheelie is a great trailer but terribly expensive. Also, the bag it comes with - unless you buy the skeleton without bag - is useless. It has loops on it and the trailer frame is threaded through it so it cannot be removed without dismantling the whole thing! and the bag is just a cavernous black hole and everything you put in drops to the bottom, and no little zipped pockets on the outside. So if you can afford a Wheelie get the bagless one and strap a long rectangular proper rucksack to it.
Re trailers and Camino routes - a trailer is no wider than your shoulders (the wheels being the widest point) so anywhere a human can walk the trailer will follow. They don't dig in but roll over obstacles so can be used on really rough trails. On the level there is no drag or feeling of weight at all! On ascents you just walk slow and steady and up you go - unlike heavily rucksacked pilgrims who are weighed down right through their whole body. On descents you go slow, steady, and lean back - should you slip it is like skiing, you just sit down. It is much more stable than a top heavy rucksack wearing pilgrim.
Will you be visiting the UK before going on to Spain? The reason I ask is that if you are I would be happy to lend you mine. I have made four trailers now, all to different designs - this is the Mk 4 (photo below with a pal 'modelling' it - an old photo as I have now put much bigger spoked wheels on it for more ground clearance).
Or - when are you going? I could post it to Lisbon, though would need to look into how much it would cost you, and then you would need to post it back to me after your Camino - let me know.
Buen Camino!!
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