I'd always regretted that paint decision, and once we got rid of the set of bedroom furniture that was in the room, it seemed like the perfect time to bite the bullet and paint the wainscotting and baseboards with a fresh coat of ultra-white oil-based paint. Just had to solve that one dilemma - how to paint the baseboards without dripping paint all over our new(ish) carpet.
When painting walls, I use tons of painters tape and have no problem, but I knew that painter's tape wouldn't be a tight enough seal to keep paint from leaking into carpet fibers. A little Google research and YouTube watching later, I had a plan....which I executed while my husband was out of town so that he couldn't get anxious about me screwing it up and getting paint on the carpet. Ha!
What you need:A metal putty knife
A 2mm plastic drop-cloth
How you do it:First, you'll need the drop cloth.
While it's an option to drop cloth the entire room, I didn't want to do that since it's a fairly large room and it would have taken several drop cloths. Instead, I used a drop cloth only around the perimeter of the room to catch any drips/spray from the paint (I used a combination of a smooth foam roller and a brush to paint the wainscotting). I used a 9' x12' 2mm plastic dropcloth. Don't cheap out here and get the 0.7 mm, which will get rips in it if you so much as breathe on it. Spring the extra $0.50 on the 2 mm drop cloth which is considerably thicker and harder to rip holes in, therefore providing better protection of your carpet. I cut my drop cloth into 4 strips that were each 2'(ish) x 12' (cut it while it is still folded up in order to cut straight lines...if you unfold the whole thing and try to cut it, good luck!)
After I had my drop cloth "strips", I laid it out parallel to the baseboards and used the putty knife to wedge about 1/2" of the plastic underneath the baseboard. To do this, I placed the putty knife about 1/2" from the edge of the plastic closest to the baseboard, angled the putty knife about 45 degrees, and pressed firmly until the plastic "caught" under the baseboard.
If you do it right, the plastic should be firmly stuck under the baseboard, protecting the carpet. Move over 3-4 inches and repeat, making sure that the plastic is taught between the 2 places you tucked under the baseboard. If any plastic is loose, go back and tuck it under with the putty knife.
Continue working your way along the wall, until you run out of wall or drop cloth. Add a new drop cloth strip, using the Frog Tape to tape the new piece to the prior piece (same with corners). I also used Frog Tape to tape the opposite edge of the drop cloth (the side furthest from the wall) to the carpet so that it would lay flat and taut while I painted and not get bunched up.
After you complete the entire room, you're ready to paint! I used an oil-based white paint and a brush to do the baseboards themselves, trying not to get too much excess paint on the drop cloth, but I certainly had a lot of drips. The next day, after the paint was dry to the touch, I just tugged on the drop cloth to pull it out from under the baseboards. There was not a single drop of paint on my carpet! Success!