In my experience you simply cannot charge enough of a security deposit to account for bad tenants. The market will not allow it. As others have said, you need to first add up the damages -- not painting unless it's necessary because of damages by tenants -- and bill for that. If that uses up the security deposit, it's probably not worth pursuing more. When you say tenants would not allow a lock box or showings, I don't fully understand that. It seems that you could put a lock box there without the tenants' cooperation. You can announce, with required notice, that you will show the property at a specific time, and you can go ahead and do that. (They can't always be home and ready to block your entrance.)
What you cannot do is make the tenants clean up their home and make it presentable for prospects who are coming to see it. I have learned the hard way that you can lose a month or more of rent because the tenants are slobs and you can't make a good impression with anyone until the tenants leave.
I don't know how to guard against this other than careful tenant screening, but even tenants who have good reputations and pay on time may be careless and sloppy housekeepers. I have the impression that they often don't even realize how bad their home looks. Some people suggest showing up unannounced at a prospect's current home before leasing, just to see how they keep the place. I find that overly intrusive and often impractical, as in the case of prospective tenants moving from out of town.
I would like to hear suggestions from other BPers on how to screen for tenants who keep a house clean and uncluttered or how to get them to clean up the house before you are showing it to new tenants. Maybe pay them for each showing if the house is clean enough? That strategy could backfire if it turns into a debate over how clean the home is.