I have been given the task of refurbing a 1985 truck tanker. It was sandblasted somewhere along the line and given no protection. Then chemicals have spilled on the surface and turned it a rusty reddish color in many areas. First acided with 10% solution. Then 3m pads to get down to fresh metal, but of course this leaves horrible lines even with the finest pad. I have then worked through the grades from 80 through 320 sandpaper. Started working with green bar with stiff pad up through white bar with flannel. Still, it isn’t great, and wow, talk about time consuming. The owner doesn’t expect a mirror finish, but I want it to smooth and line free at least. I have even tried glass beads through a blaster for a starting point, but am still disappointed. Any good advice would surely be appreciated…Thanks in advance for your response.