People are misunderstanding the problem. So it's clear that a majority of people think Hillary is untrustworthy. But let's break that group up. A good portion of them are unpersuadable: partisan Republicans who answer negative to any democrat they are polled on and those people who have independently researched and come to the conclusion that Hillary is corrupt,. They aren't important tbh. However there is a large group of people who are less interested in politics, and don't know the ins and outs of every scandal (because they are normal human beings). With the current news cycle these people's understandings of the various scandals is that Hillary did something dodgy (after all, no smoke without fire?). Seeing as this is a majority of voters, this must include people who voted Obama so they obviously aren't just partisan anti-Democrats. These people are the ones that must be persuaded for a positive win (i.e. If the campaign is just a scorched earth attack on Trump, Hillary would probably win but her presidency will start off unpopular and she won't get any coattails).
Spot on.
As for the scandals themselves, have one bombastic press conference to apologise and put the issue to rest. Then leave it to proxies to rubbish all claims and make even the more grounded of them seem like Vince Foster tier.
I'm not sure this would accomplish anything other than to keep the issue fresh in the public mind. Ignore it, stay above it, stay on message, and pray it goes away on its own. Proxies and surrogates do help, however, as long as they aren't too obvious.
Dwelling on this too much makes the Clinton campaign sound like Trump denying that he has very small hands.