The home I recently purchased has venetian plaster walls in one room. Although I love the look, the color is way too dark for me. The former owner told me I could paint over them. I just started priming over my walls in order to paint them a lighter color. When I got one wall mostly primed, I noticed bubbles popping up on the wall. They range from as small as the tip of an ink pen up to dime size. They are squishy when you touch them, as if the wall is rubber and someone pumped air under the plaster. Sanding over the primer and painting again just produced more bubbles. What can I do?

Going to be using Benjamin Moore oil-based solid color stain on an addition and the remainder of the house. The cedar clapboards on the house were replaced about 15 years ago and were never stained or painted. The addition will be new cedar clapboards. There are exposed square head nails on the house that appear not to have rusted. I plan on using a siding cleaner, then lightly pressure washing the old siding. I have several questions for which i've gotten conflicting info: 1) Do i need primer on the new clapboards 2) Do I need primer on the old clapboards 3) What is best to clean the old clapboards 4) Can I stain right over the nail heads Thanks