First, we had to demolish and remove the old wooden railings. The 8x8 posts were sound; all we did to them was reinforce their attachment to the sundeck, and add new metal support brackets for the new railings.
Then, we assembled the new railings, using pressure-treated 2x4's and aluminum balusters. The assembly was done on a pair of sawhorses, and held together temporarily by the orange strap clamps you see here, while the assembly was being placed into the newly-installed support brackets on the existing 8x8 posts.
All done except the stain on the new wood, which has to wait until the lumber has dried out some. The sawhorse shown are where the railing assemblies were put together.