Here's the template I used in my emails, to give you some inspiration.
My name is bfollinprm, and I've recently completed my undergraduate studies and am looking to continue my graduate work by applying to grad schools for this coming fall.
I've spent several years both during and after my undergraduate years working with Professors (1) (at university A) and 2 (at university B) on CMB analysis/simulation and enjoyed the research immensely. Projects I've done include instumental error analysis, Fisher analysis of hypothetical experiments and their ability to measure the B-mode, and a technical paper on extracting cross terms from adding interferometers.
I've applied to grad schools with the intention of continuing this line of research and learning more about the theoretical ramifications of the data CMB experiments collect, and your group is what really drew me to apply to this graduate school. I was wondering if you would have any open research opportunities next year that would fit my research profile? Both professors (EMAILS) should be willing to speak to my past experience and work ethic. I've included a CV just in case.
I got some good responses from this email.