I just usually rinse the fruit gently and then freeze it to burst the cell membranes. Thaw a bit before using. You don't need to mash up your fruit.
Add the fruit to the primary, not the secondary. Fruit is a great source of nutrients for yeast, and you wind up with a faster fermentation and a cleaner-tasting mead.
Look for Curt Stock's article on melomels in an old BYO. Best advice anywhere.