Vinegar is typically used to remove rust. If it is not rusty I would use the lye. As far as sandblasting that is not recommended. Wire wheels, sandblasting ect. can damage the surface and it will not season correctly. Wire wheels can be used if they are fine wire and stainless steel and not brass. The brass will transfer to the cast iron surface. I have seen lots of skillets that have been cleaned with a wire wheel and original surface is messed up and the seasoning will not "take".