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.
If the problem is that the solder is not "pulling" into the joint it may not be hot enough (try using MAPP instead of propane in your torch). But I find the biggest help is to use lots of flux (aka soldering paste). Go crazy with it, use it really liberally.
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.