Depending on the liner quality, just riding them will help mold them. If they are really good quality liners, they will last with a bake or two. From what Angry said, sounds like the shop gave you the perfect advice.
I always go to a boot fitter anyways for new boots., I don't get head molded, but I have him add a little cork heel lift to my superfeet red insoles, and a top-of-the-instep pad to help my slightly smaller foot from moving around. He always does it for free and I tip him.
Boot fitting is not often done for soft boots, but I think for some people it could help
Digging this old thread up, but what does this top of the instep pad look like? Where does he insert it? I have wide feet, but they're low volume. So I have a ton of room above my foot. Cranking down laces makes the side of my foot hurt due to the abnormal width in the middle of my foot. Got my perfect length boots, wide enough but now I have a volume problem