Spend a night chopping trees or mining in a black forest and killing the hundreds of grey dwarves that swarm you. Bonus points for doing it within range of one or more dwarf nests.

You'll be rolling in resin after one night, with a bunch of extra wood and stone besides.

Alternatively you could make one of them fancy auto wood/stone farmers using a dwarf nest, as that would be a passive way of getting resin too.