We ran copper by the tractor trailer loads during the 40 yrs we were in the mechanical contracting business.
My take on soft soldered copper tubing.....
-use a fitting brush to clean the ID of fittings. Cheapest ones have a simple wire loop handle and are about half the price of the ones with a wood or plastic insert in the handle. The brushes don't last long enough to need any sort of fancy handle. Spin the brush in one direction, not back and forth, and it will last longer and do a better job. Easiest way to clean a lot of fittings is to take a pair of side cutter pliers and clip the handle loop off the brush so you can insert the shank in a cordless drill. About 2 seconds per end, and the fitting is clean.
-use sand cloth or sanding screen (preferred) for cleaning the OD of the tubing. Its too easy to contaminate an OD brush and not realize it until you have multiple leaks that have to be taken apart and re-cleaned. I never allowed anyone to use an OD brush regardless of their preference, and if we had one leak in a thousand joints it was rare. Use the sanding material in a shoeshine motion. Don't grab it in one hand and wring it around the tubing because you'll end up with the oils from your hand transferring to the sanding media and from there to the tubing. Natural oils from your skin are the #1 cause of leaks in soft soldered copper.
-Nokorode (no corrode) paste is one that's been around for years. Its a very weak paste in that its not self cleaning. Pastes which are strong and self cleaning tend to keep on cleaning, or attacking the surface of the tube or fitting over time. Easiest way to spot joints made with self cleaning paste is an accumulation of green crud around the joint a year or so later. Some will say you avoid that by wiping the joint down with a wet rag after soldering. To that, I ask them how they wipe the inside? I picked up a tin of paste at Lowe's recently, marketed by Lenox, the bandsaw blade people. As far as I can tell, its identical to Nokorode. Probably made by them since Lenox isn't in the chemical business AFAIK
. Pick up some acid brushes to use for applying the paste. Apply sparingly to both the fitting ID and the tube OD.
-can't make any recommendation for a good soft solder. We didn't do any potable water piping, just hot and chilled water for HVAC and process applications, so we used 50/50 (lead/tin as mentioned above). If you can find a roll, its the easiest to use. Probably can't, but the general opinion seems to be that there are decent lead free solders on the market today.
-M copper should be fine for your air lines. I'd use a Bernz o Matic type torch for this work. They'll work fine and the heat is easy to control. A Prestolite torch works well to, but too much money for occasional use. Avoid the temptation to use oxy acetylene even if you have it. The heat is too hard to control on small tubing, even for someone who does it for a living. Burning the paste is a sure recipe for a leak.
-assuming you'll be using threaded valves at your takeoffs, make the joint at the tube and male adapter before screwing the adapter into the valve. This keeps the heat off the valve and off the pipe dope or tape at the joint. People who run copper every day tend to avoid using female adapters to the greatest extent possible, because they're far more prone to leaking than male adapters. To follow this principle, you need quick disconnects with female pipe threads. Female threads are the most common, but they're available both ways so its worth mentioning.
Unless you're absolutely sure you won't want to modify your piping sometime down the road, the main line should be mounted a couple inches clear of the wall, or hung from overhead, rather than clamped tight to the wall. A bit of clearance will allow you to take a compact cutter and cut a tee into the main anytime you want. Tight to the wall, and you end up trying to cut the line with a hacksaw and pry it away from the wall sufficiently to clean the tube and make the joints. If I had only one tubing cutter for small tubing, it would be this one. http://www.toolup.com/ridgid/40617.h...m=ridgid+40617
It will handle anything up thru 1" copper, works fine for all cutting on a small job, and gives the necessary clearance for cutting in a takeoff in a tight area later on.
One final thing is reaming of the tube after cutting. I've used the built in reamers that are a part of some tube cutters (worst type of all), rout-a-burr deburring tool (better), and my favorite copper deburring tool which is a pocket knife. On air lines, you're reaming primarily to keep any moisture flowing rather than having a series of steps that act as small dams for moisture. 5 minutes of practice with a reasonably sharp knife, and you'll cut the burr right out with a single twist of the tube. Ream before cleaning as you need to be able to hold onto the tube while reaming.