My brake booster vacuum nipple is between cyls 2 and 3 on my inline 4 intake manifold and looks like it's distributed pretty evenly. Think about it, vacuum brakes are the biggest vacuum load on the engine, they want it to be even across the cylinders so the o2 sensor can adjust for the "leak" and still have it run right.
I use an old plant food sprayer the wife got for my h20 decarb, it holds a quart of water, pumps up with air pressure, and has an adjustable doohickey on the end that goes from spray to mist. Just spray it across the horizontal throttle body. Don't do it enough really.