Every house is different. The loose paint on your house can be a result of a dirty substrate or moisture problem. Both cause peeling paint. Both must be fixed before painting. When paint is peeling, primer will not stop the process. The loosely adhered paint must be scraped and then it should be feather sanded to break down the edges so that bridging doesn't happen when you repaint. Bridging is the edge of the old paint where it meets the undercoat or wood. When a sharp edge is left there,the paint on that edge is super thin and will crack and peel off in time. You can read the label on Peel Stop and decide if that fits your need. Other than that, removing loose paint is mandatory for a professional, long lasting finish. Power washing cedar and other wood products can be detrimental if done by inexperienced persons. Damaged wood is ugly when painted. Ask your choice of contractor if they know how to power wash wood surfaces. Most pro's do not use the "power" in a wash, just the soak and rinse feature. If he is using the power wash to remove the paint, he's damaging the wood surface and pushing water deep inside so that the paint will peel again in the near future. I've seen that a hundred times right here in my own development. Peeling paint; power washed house; same schmuck doing it. It sure keeps him busy though. LOL Michael

Your ranch is never going to be a modern farmhouse. And painting the brick was a mistake for 2 reasons: paint on brick is a maintenance pain and can actually lead to degradation of the brick since it seals the pores. https://masonryadvisorycouncil.org/wp-content/uploads/2020/10/Staining-Brick-Masonry.pdf that colour is just wrong on your brick. Your brick only looked "poop brown" because the siding was yellow. So first, get that paint off of it and save yourself future maintenance woes. Then, if you still don't like the dark foundation with a your new alabaster siding, investigate a proper masonry stain for your brick. But not white. Something darker than your siding to ground and anchor your home. Cancel the black windows and charcoal trim. Have a look at the SW Alabaster page for co-ordinating colours. Something like SW Half Caff might work. But before you choose anything new, collect samples of all your current materials-- brown shingle, Alabaster paint, cedar sheathing and put them side by each, preferably outside so the lighting will be correct. Put them somewhere you can see them often. And each time you walk by for the next week or so, look at them and think about how they go (or don't go) together. Then, if you're satisfied that the cedar is a good idea, add some colour samples for trim and repeat the process. Take away any sample that looks off. Once a sample is eliminated, throw it away. The fact that it might be ok in some lights does not negate it's "off-ness" in others. You should be able to come to solid conclusions about colour inside a week. If you were a professional, you could do it much faster. But that's why they are professionals. Us mere mortals are better off choosing colours based on experiencing them together in the space where they will live.

@Seabornman - How did you work with those "surprises"? Were you able to match the original siding? Or do you more often have to look for a custom (ie, expensive) solution? We will need to remove siding from the area where the addition will attach; I'm hoping we may be able to salvage some of it to fill in for those inevitable surprises....

Where are you (just curiosity, I’m sometimes in Eastport) Generally I’d say oil primer with latex topcoat is still the way to go with cedar. Depending on where you are head to your closest Sherwin Williams store- they tend to have really knowledgeable staff. No to weathering, bright wood holds primer better than grey wood. Rough versus smooth is just aesthetics. Finally since you are painting, why not use cement trim?