Well first you will need a browser extension like Foxy Proxy to create accounts behind proxies for Tumblr and free email accounts, also a cookie cleaner extension to clean your cookies between each account creation; something like Click&clean (don't forget your LSO cookies: Flash cookies) then a bunch of shared proxies authorized by IPs, Google it. Try to find a small supplier, less risk for those to be overused at Tumblr. And then a Tumblr bot like the one rootjazz sales.
Its a bit of a complex scheme, you should try to find a recipe somewhere, search this forum to start with.
Good luck