When I import a list I do it using Import sites panel and not directly from amrx file. That's because when you use import from AMRx file AMR do not test the sites before adding.
Adding them through Import window will make AMR test the sites and do not add dead sites,broken templates etc. So fromthose 70K list I suppose you will get around 4-5k alive and working sites. Another problem are wordpress blogs which are seen as valid but are not article directories so will not be able to post.
Anyway, after you imported alive sites you simply start to create accounts then check those in email stats and run a Forget password and then confirm button to get the password for more sites then refresh. Also I suggest you to check all failed sites and try again to create accounts you will get another 10-20% working websites. Now that you have accounts create a text article and submit it. Check all the websites that worked and do a live links report. You will get websites that auto approve your article.
Now you have a working article directories list. Blacklist the websites that haven't worked and not delete them. If you ban them when you will try to import them from other lists will not work but if you simply delete them you may added again as may be packed in other lists so you will have to deal with them many more times,.