Our end goal is to mud over the existing plaster walls/texture to create a smooth finish. Before this we want to repair several hairline cracks to prevent them from recurring. After scraping open the hairline crack we plan to add caulk inside the new, wider crack, but not fill the space all the way to the surface, leaving room for a sandable Durabond to bring it flush to the surface. Our thinking is that the caulk would allow for flexibility at the back of the crack and the Durabond would allow for better control of the surface sanding process. We would appreciate any insight into this process.
Fiberglass tape and a couple coats of compound will give you the best results.
Just a thought not sure how textured your walls are that you're trying to smooth out but sometimes this can be more work and leave you with inferior results instead of just taking it down and replacing with drywall.