That's a great plan
I agree it would help to have an idea of where you are travelling from
Is it weekends only because you have a day job? If not, you may get a *lot* more offers if you can do a week at a time - with a lot of jobs, someone who is only there for a day or two is a drain rather than a help. If you can get someone for a week, then by day 3 or 4 they are starting to make a real contribution to repay the effort in getting to know them and teaching them the job
We are very happy to have helpers at lambing time, shearing time and hay-time - but for lambing time especially, one or two days is no use and we can't spare the time to show people the ropes. If they can come for several days a few times, or for a week or two, then we can invest the effort up front because they are really helping later on
Of course, some people may be happy to give you a day's training in something new in exchange for a day doing something you already know - like painting fences
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When I was WWOOFing, I mucked out a *lot* of winter pens on a *lot* of farms, and I did a *lot* of weeding in a *lot* of different places. There isn't anywhere I WWOOFed that I didn't learn something new, though