I have dry fired my P89 ALOT and have made the trigger pull much sweeter over time. No problems so far but I do use snap caps sometimes. Probably best to use them.
I have never used HiViz on a pistol. They work great on shotguns thou. I have heard of them busting on pistols if you use it alot.
May i recommend Meprolite Sights. They are tritium sights and I love them on my p89. Easy to see white sites in daylight and in just the slightest low light and they pop for easy sight picture.