SMD can be done just as well with a heat gun (used carefully), or a butane Weller soldering iron with the "heat blower" (not the torch) attachment.
Some people have said that just adjusting the temp on the toaster oven manually while holding a stopwatch works well too, it just keeps you watching it.
And simple SMDs like a SOIC-8 are easy to do with a soldering iron. Some use a fine point iron, others use a wide, blunt point and drag the solder ball across the pins. Some people got good at doing even fine pitch ones by hand with the blunt point too.
The trick with the buck converter is going to be finding the right inductor. For starters, saturation current must be a healthy margin above 8 amps. The resistance of the copper wire should not create excessive heat, a hot inductor has a substantially reduced saturation current as well as inductance. And the inductor needs to have enough inductance to satisfy your ripple limits at the freq you've chosen at the max current you will be drawing.
Feel free to check back with us with questions of inductor and transistor selection.