Good idea with the holster on the dash.
You can also use something like this:
to keep the gun from moving around while driving.
While OC'ing, I believe you do not have to inform the officer, as the gun is 'in plain sight.' If your concealed, then you definately have to, but I'm fairly positive you do not have to notify while OC'ingand as calmly and politely as possible inform the officer about the handgun "sir/mam i'd like to inform you that i have a firearm on my dash"