It's called awareness. If you insist on open carry you have to pay extra attention to those around you...ALL THE TIME...and use a holster with some form of retention device. Even those who carry concealed should exercise above average awareness.
I disagree about potential bad guys not knowing how to operate a Level II or Level III holster. Criminals practice this stuff...and probably more than the average permit holder practices! The retention features are there to slow the would be gun grabber down long enough for you to react but you must react swiftly and surely or you will likely lose. Anybody attempting to grab your gun probably knows how to do it quickly and violently and you will have to fight like your life depends on it.
Carefully consider the consequences of open carry before you exercise that right. It may have a place but in my own personal opinion that place is very limited and somewhat risky when compared to competent CCW.
IDPA Member A00640
Founding Charter Member - Middle Tennessee Shooter's Club