Built 1900, Rear of house south west facing. All the wood is sound original pitch pine (still oozing resin in places). The front is fine but the back with the sun on it sheds paint and needs re-doing every couple of years. I have gone back to bare wood, primed, undercoated, glossed and prayed to the gods without success. It's like the Forth bridge. Is there a paint or process anyone can reccommend? The usual brands don't seem to stick. Also the grain is opening up, on some of the frames and ledges up to 1-2mm. Is there a filler primer similar to that used on car body work ie fills but remains soft enough to sand easily. Many thanks