Moguloid solidified, is it still usable?

We bought an old bottle of Moguloid block seal (to fix holes in the cylinder head). But the contents were no longer liquid and was solidified – like a rock. The shop owner ended up giving it us for free because of this and told us to hit it and break it to powder – I assume the next step is to put it in water so it liquifies again?

Anyway, will this work? Do we add water to it? How much water?

Thanks