@skippy. Here is a link to a few articles concerning how the red-light therapy helps heal tissue after undergoing radiation: Just right click and click on "go to."
https://blog.tracydonegan.org/blog/how-red-light-therapy-is-revolutionizing-cancer-support-relief-for-oral-mucositis
https://www.redlighttherapydigest.com/red-light-therapy
How often should you do therapy?
The "how often" varies wildly depending on your specific condition. Most people doing Swallowing Therapy (with a Speech-Language Pathologist) are often asked to do their exercises 2 to 3 times per day, for about 10–15 minutes each session. As for me, I bought a Neutrogena Red-Light Wand (older) off eBay for $20. They still have a few on there. In the morning and at night before bed, I would wave it around the back of my throat and also on the outside neck area. You cannot feel anything, not even warmth...so it feels like you aren't doing anything! Maybe my function would have returned in time without the red-light, but it is proven to accelerate healing.
I am so sorry you got a double whammy. Keep up the good fight! I pray you regain your function.