Hi,
I've done hand soldering with both very thin solder and also solder paste.
The biggest problem with using an iron on those small parts is holding the part down when you lift the solder tip. The solder sticks to both the part and the iron tip, so when you lift the tip often the whole part comes up with it and stays on the end of the tip instead of the board. This means you have to have a way to hold the small parts down while you hand solder. If you can do that you are good to go. I even used Elmers glue a couple times before soldering giving it plenty of time to dry first 
With the heat gun the little parts stay there pretty well with gentle air flow, and the solder paste melts and distributes nicely.