Question about using expired Tumblrs

I've acquired some expired Tumblr blogs.

1) How much (if any) content should I add to them before using them for link building?
2) How about a mild GSA SER blast for these blogs, should I do it or is it a waste of time as they already have some authority on them?

Anybody? Damn, should've gone for that how to make money online type of stuff, at least I would've gotten my share of mockery.

Add some content and they're ready to go.
Blast'em with full power mate!