Most, if not all, .35 Whelen die sets have the tapered expander. So, in theory, you can just run them through once. I say "in theory" because, as with everything in life, there are some failures. Bent, crushed or collapsed do happen. If you wanted to use an extra .338 or 8mm expander, more power to you so go for it.
I stopped when .35 Whelen brass can just be ordered. I did several boxes but gave up. It is nice to know that I could reform if I had to.
If you want to because of having lots of left over .30-06 just jump right in. It is one of the easiest conversions. But do check to make sure your dies have that tapered expander.
Also put a SMALL wipe of resizing lube inside the case neck for ease of reforming.
Happy loading.
