I don't think I'd sandblast it. I think you'd run the risk of wearing down the detail, even with walnut shells. I'd opt to strip it in place, or take it down and strip it outside and re-install afterward. I'd use one of those peel-able strippers to try and get the paint and gunk out of the bead. A tedious, but do-able proposition, at least I hope so as I have a whole room and ceiling that's on my list for that treatment this Spring. Fortunately mine isn't painted, but the varnish has become blackened and needs to be removed. If you ask me again after Labor Day, I'd have some experience to offer, rather just a plan. Molly~

In addition to the nails, glue it with PL Premium adhesive. You might want to reconsider painting the Azek. A good quality paint will last for many many years on this stuff. And it will be much easier to keep clean.

If there are knots in the wood, you will have to use at least 2 coats of BINS and then putty over the knots and then prime them and paint them. A LOT of work.

We have given thoughtful consideration to all suggestions - thank you. I would like to ask another question - not sure of Houzz protocol about starting new thread so forgive me if I err here. We have a beautiful elk antler chandelier and thinking about where to install in the new house ... great room is obvious choice. We could hang it from the middle beam in the room - other opinions? Here is a pic. Size is approx. 42" side-to-side and it is about 28" high ... without the chain. In this picture we don't have a very high ceiling in the entry so had to squish it close to the beam.. PS To give you all an idea of our aesthetic, my husband is a bow hunter and ranch/hunting style house is naturally where we lean ...