<p>Is there a way to automatically apply a theme/template/style to all controls of the targettype, so I don't have to specify Template=..., Style=... on all controls?</p>

I thought there was a way to do this by just omitting the x:Key attribute, but that doesn't seem to work anymore. Based on some googling it seems to me like you're best best is to create a custom control library of your own that has a themes/generic.xaml file that defines your custom styles. Then you can use your own elements that are styled properly (MyButton instead of Button). Either that or
stick with the Style property
.
Some example of this
here
and an alternate approach using themes
here
.
Update:
Just found a really good example of this
here
(I think you might have already seen it :).