I wouldn't just go for the PR 0 sites. Some websites might not have a PR, but still not be harmful, such as new blogs etc. Identifying bad links is something which does take a lot of time, though. Basically, I wouldn't recommend to just take a list of backlinks, sort by PR and disavow them. For instance, have a look at each backlink's anchor text. Google does recognise whether or not the anchor texts look over-optimised. You should also have a brief look at each website's content: Is this a website you'd like to link back to you or rather not? In case you come across some Public Relations or affiliate websites, make sure their links are nofollow - if they are not, disavow. Big Public Relations or affiliate websites may do very well PR-wise, so you might not be able to identify them when just looking for low PR sites when reviewing your backlink profile.
Ever heard of Link Research Tools? They do have a Link Detox Tool. It's quite costly though, but it might help you to prioritise your links within a short amount of time. It crawls all of your backlinks and prioritises them according to their algorithm, so you know which ones to disavow first. Though I'd never trust a tool's algorithm, this one seems to be pretty accurate, and it helped me a great deal recently when dealing with a client's website to prevent from penalisation.