It's self explanatory when you try to use it
you set it to fold a little then work round the arch a few times
then adjust it in a bit more
then swing it more
and repeat
just don't try to do too much at once.
also, you may want to warm the paint inside the lip with a heat gun as it's less likely to crack?

I suppose I could lend this one out if people arrange a courier collection
but I would need £300 returnable deposit