My idiopathic PN hasn’t been diagnosed as SFN, but I get tight as you’ve described. I seem to take a lot of days to recover from even the most simple daily tasks or movements that may have used a new muscle. PT has helped me so much with gentle exercises and some of their massages to get knots out. Even with safe stimulation and supervision, the stretches still sometimes leave me sore, but I’ve found that my recovery times improve. It’s been extremely helpful. I complete a round, try hard to keep up with the take home exercises, but generally regress a bit, then have my PCP refer me for another round of sessions. I have a co-pay, but to me it’s like paying a personal trainer with more medical knowledge being a physical therapist so that there’s better understanding of my goals and medical limitations. I honestly don’t know where I’d be right now if I hadn’t had PT’s over my 6+ years of living with this.