Wearing a good-quality breathing mask (Paquin recommends using organic filters in the mask), apply Jasco Premium Paint Stripper to the beam with an old brush. Wait 30 minutes before scraping it off. A second application of stripper may be required for stubborn paint residue.
Using a lightweight (7 lb.) belt sander with 80-grit sand paper, sand the beam surface to remove the paint remaining after the stripping process.
Switch to a random orbital sander, again with 80-grit paper, to even out the surface.
Use a "Multi-Master" edge sander (also made by Fein) to sand right up to the edge where the beam meets the roof and walls. This is a remarkable, and essential tool, as hand-sanding the edge areas is simply not practical.
Finish sanding with the random orbital sander and a fine grit (120-160) for a smooth surface.
The last step, and the easiest, is sealing and staining. Paquin tested a wide range of products to get the look he wanted, and then decided, for simplicity's sake, to use the same products both inside and outside. First wipe on Behr Wood Sealer & Finish 'Redwood and Red Cedar Wood Tone,' which waterproofs the beam. Quickly wipe off any excess, then immediately wipe on Cabot Semi-Opaque Stain '6133 Red Cedar,' and remove the excess. This combination seals and waterproofs the beam and lightly enhances the grain without overemphasizing it. Of course, other approaches are possible to produce different results, depending on personal taste.