I have one of the Harbor Freight guns and it works great for spraying
laquer and other finishes. It is just not the right tool for the job
for spraying a house. It works great for laquer because it puts out a
very fine atomized mist. In the slightest breeze this mist will be
all over the place and you will end up using a lot more stain than
necessary. An airless sprayer is the right tool for the job but even
an airless sprayer will not bond the paint as well to a house as a
roller or paintbrush. An airless sprayer doesn't break the surface
tension of the underlying paint as well as a roller so even with an
airless sprayer I have heard it is reccomended to "back roll" a house
after it has been sprayed. By "Back rolling" you will get better
adhersion and your paint job will last longer.