Over the years I've soldered several remodels worth of copper pipe (water and hydronic heat). I'm not great, but I get the job done, until I have to add a brass fitting. For some reason, I can't get the solder to suck into the joint. Does soldering a brass fittings to copper pipe require a special technique?
Very Important Make sure the joint is really clean when you solder - so use emery cloth or sandpaper to remove any contaminants in your solder joint and flux the joint prior to heating. I like to wipe the joint with acetone before applying flux but I'm anal retentive like that.
Also you might want to consider using MAPP gas vs propane - those brass fittings take a lot of heat before you will get solder to flow into the joint.
I just had the same experience. What i figured out was, whereas they say to concentrate your heat on one side of the fitting until it is hot enough for the solder to flow for copper, i had to heat all around the fitting for brass. Once I did that it flowed just like copper. Like the pros are saying, it took more heat for it to flow properly with the brass.