Pesky

First post but appreciate advice in forum, hope I can return the favor after I have gone through the process myself. How do I word request for LOR to professor whose group I will also be applying to ? I plan to apply, and hope for admittance, into engineering group of PI that I did a summer REU with and I am concerned with how to approach for recommendation to other programs/schools while also promoting myself to his group. Suggestions? Thanks.