Mturk manuals are junk and very hard to follow. HIT data cleansing is the biggest issue. Instead of using the command line tool, use their API to integrate into your app, as it will save plenty of time down the road...

To "weed out" ineligible workers, try this approach: 1. Post a bunch (1000-5000) of cheap multiple-choice HITs. 2. Allow no more than 10 hits per worker. 3. Each hit to get 3 responses from different workers. 4. Review answers, compile the list of "good" workers, blacklist the "bad" ones. 5. Post another bunch of HITS, make them available for eligible workers only (found in step 4), this time the HITs might be more demanding, individually review results for each worker -> the best ones go on your "preferred worker" list. 6. Repeat steps 1-5 as necessary.

From then on it's fairly safe to rely on mturk workers from your preferred list.