Mine is an insertional Achilles tendonitis (so right where the tendon attaches to the heel). Here is what I have done:
-Took 4 weeks off from running
-During the time off, I used my Theragun twice a day on my calves and also spent time with the foam roller. I really tried to loosen up the calf muscle via massage
-Once I started feeling a difference with massage, I started doing modified eccentric heel drops (where my heel only went done to the floor, instead off off a step)
-Based upon some reading, I have also started trying some isometric "stretches" on my impacted calf. My heel feels better after doing a set of them, so I have kept them up
-I have also added some ankle/foot mobility stretches with a lacrosse ball. I put it under my 4th/5th metatarsal and then twist at my waist for 90 seconds. It also really seems to help loosen it up
All of that to say.....it is still stiff when I run but at least I am able to start rebuilding my mileage. The pain never gets higher than a 2 or 3 (out of 10) when I run but it also never is 0 when I run. I don't experience much pain throughout the day but, if I do, then I take a few minutes to massage my calf (via theragun or roller).
Overall, massaging my calf has had the biggest positive impact. I'm not sure how much the modified eccentric heel drops are doing but I keep them up.