Hi send a letter to frank and tell him about the hybrid strings I use on my guitars. Mention our mutual friend and how I’m glad he is playing guitar again. Give some benefits of the strings in bullet point form and let him know to call me soon. Sign it with my name joe. Feel free to come up with filler details for the letter.
Hi Frank,

I hope you and your family are doing well! A few days ago, a mutual friend of ours mentioned you were picking the guitar back up. I’m really happy to hear that! He also mentioned that you were considering a different set of strings from what you used to use. I remember you mentioning some time ago that you wanted a bit heavier on the bottom strings, but that the top strings were too hard to bend with that set. 

I want to let you know I went through the same things, and found a great hybrid set that mixes the top 3 strings from a set of 9s and the bottom three strings from a set of 10s. So you can have the best of both worlds:
• The heavier strings stay in tune better, which is a good fit for your type of playing.
• The bottom strings sound fuller, which can be helpful in a single guitar group.
• The lighter top strings allow you to do some bends without hurting your fingers.

Let’s get together in the next few days; I’ll bring one of my guitars with the same type of strings, and you can try them out to see if you like them. Give me a call, and we’ll set something up.

Talk to you soon,
Joe