I actually use a small brush most of the time, It seems scary and long winded to begin with but its actually easier, faster and produces better results.
I said to start with a large brush size and then get smaller, thats what I do, I pick a brush size that lets me move 5-10 points at once then after the disp is roughly right I almost instantly downsize to 1 point brush size.
As a rule of thumb I never ever touch the smooth tool. It just doesn't work and if you try to smooth on a non perpendicular axis it really F***s your displacement.
The Subdivide button:
Sometimes I feel the urge to use this button, its quite intersting but I rarely keep its results. I select all the faces I want to subdivide and hit CTRL+S (Save) then hit the subdivide button. What it does is it smoothes all your corners out to what it thinks is right, sometimes it gets it spot on, some times it looks horrible. If its horrible I just hit CTRL+Z and shudder before using the normal brush tool. When I made the arch in the earlier screenshot the dubdivide tool was very usefull, I selected all the faces and subdivided them, it did almost all of the work for me. I then only had to go make it a more natural looking shape and tweak the edges.
NB: This button is not for beginners!