I have a couple of swing and Latin comping rhythm exercises on my site.
http://frogstoryrecords.com/
Look under the Comping section. In the examples, the X note head represents a muffled stroke.
And here's one exercise that I had my Berklee students do: Open Leavitt's Melodic Rhythms for Guitar book to somewhere near the middle. The book is organized by number of attacks per measure, so around the middle there are not too many attacks. Now strum the chords using the rhythm of the melody.
Of course, you can do this with any song, but having a bunch of songs with just a few attacks per measure is the best place to start.
Steve