Setting Velocity for a selected group of notes

Not sure about PRV since I don't use it..... but in staff mode.... right click a note and the drop down offers that option.  I think you can also do that with a group of motes by highlighting the group.
 
It's been a very long time since I worked with midi at the basic level. I used to do it alot in my early days but now tend to work with audio tracks mostly.