I think a number of things are worth considering.
Even before thinking about weekly matchups, a defensive back needs three specific skills (among others) to be able to make plays on the ball -- coverage instincts (whether zone or man), recovery speed and ball skills. Most of that can be gleaned from scouting reports before they reach the NFL if you're not a big college football person and by watching games and tracking stats. Without those skills, a defensive back isn't going to rack up PDs unless his opportunity is extraordinary.
Generally speaking, you'll be looking for man cover corners over zone cover corners because the man corners are likely to be tighter in coverage more frequently. Skill is more important than scheme for safeties, though a solid cover free safety who gets some extra chances in man coverage on tight ends or slot receivers are worth watching.
Specific weekly matchups are important, especially for borderline cases. Offenses that throw more often than they run and/or are more likely to be far behind early will provide much better opportunity than those that are ball control/run offenses or won't be forced to throw by an opposing defense. You may also need to consider how balanced an offense is (i.e. is the WR2 close in talent (or likely targets) to the WR1) and whether a given DB prospect's teammates are likely to be thrown at more or less often (i.e. avoid a shutdown corner, target a new or rookie corner).
Linebackers most likely to hit double digit passes defensed include MLBs and WLBs that play a lot of zone coverage and are talented enough to be used in man coverage on TEs and RBs. That usually means Cover-2/Tampa-2 guys are the best options, but it's not absolute.
In the past, you could also target certain stadium stat crews that were much more liberal with PDs than others. That's not nearly as easy as it used to be, however.
By now, you're probably thinking that all of this is silly. And, to some extent, it's paralysis by analysis. Unless you really want to get to the bottom of every matchup angle, it's worth having a cursory idea of what kind of talent a player has and how many pass attempts they're likely to face. If you're not sure, questions are always welcome and there are a number of tools and stats available at FBG to help determine matchups.