I need to make a 2 pc mold for a part containing a helix. By nature, the helix creates undercuts as shown here:

Obviously, I can't have these and expect the part to release from the mold. We do a lot of similar molds and currently fill in the undercuts manually. As you would expect, this is very time consuming and cumbersome. I am hoping to find an easier way to fill the undercuts. The geometry does not need to be precise, but must transition smoothly. I have attached the part files I used to create this. Any help would be immensely appreciated. Thank you!