If you've had a lot of trouble with staff greifing, don't take applications. Pick your OPs from your player base after learning who's mature and acts accordingly. Make sure they've played actively for over a month or you will continue to cause trouble.
Genuine people will stick around and the ones just looking for power will notice they have to earn it and everything they lie about on applications will become apparent.
But that's just my personal advice, it's your server so run it how you like
