I was able to build a cheap SMD soldering station with a surplus electric hotplate (like those used in chemistry classes now that Bunsen burners are not considered safe) and a PID controller from eBay. Total cost under $50. Some people use toaster ovens--that is probably better than the hotplate, but you still need precise control over the termperature profile.
The PID controller gives you the ability to program in the proper temperature profile for soldering. Setting them up can be a pain, but you can build your own with an Arduino, a thermistor, and a relay if you want and you would have absolute control over everything and probably a better understanding of how it works than with an off the shelf PID controller. I sort of wish I had gone that route because the PID controller does not handle the thermal latency all that well--at least not the ont I bought.
Design your board, have it fabbed by your favorite PCB house and order s stencil at the same time.
Align the stencil with the pads on your board, and clamp it in place. Squeegee solder paste through the stencil, remove the stencil and carefully place your parts. I find it best to tack one or two leads in place on the smallest parts because I need to apply some heat from above as well as below and I use a heat gun for that, but radiant heat from above and below would be better, hence the toaster oven idea.
The SMD soldering profile is something like a preheat period of several minutes, a rapid ramp up to soldering temperature, followed by a cool down period (just look at any SMD IC datasheet in the back pages where nobody reads) for the profile. Cooling should be slow enough to not induce thermal shock yet fast enough to not induce thermal shock. In other words, there is an optimal range for cool down rate.
I find that just removing the board from the hot plate works well enough for cooling, but you have to be careful taking it off the plate or parts will go flying . I find 4x4 inch squares of 40 to 60 mil aluminum "baking sheets" placed between the hot plate and the board, with some sort of non-heat conductive handle works a lot better than trying to grab the board with pliers to get the board off the hot plate.
I can solder a 4x4 inch board fully loaded with SMT in about 5 minutes. It would take me hours by hand. Plus, if I ever get crazy enough to try it, I can use BGAs as well--you're not going to do that with a soldering iron. If there's interest I can post a picture.
