When tilt/shift are applied, it alters the incident angle of the light hitting the metering sensor so you'll get over- or under-exposure depending on the direction of the tilt/shift. The easiest option is to use Live View, which meters based on the imaging sensor, so T/S doesn't affect it (plus, you can zoom to 10x for focusing). If you absolutely don't want to use Live View, you'd need to meter with the TS movements at zero, then use those settings after applying T/S.
Another thing to try is a shifted panorama (shift in combination with 45Â° and 90Â° rotation, you can stitch 9 shots together).
Have fun with the lens!
Always use a tripod, it's almost impossible to use TS-E lenses without one, in fact, I have never hand held a TS-E lens.
Handholding is possible with some practice (at least for shift, maybe not for tilt). This shot was taken handheld:
EOS 5D Mark II, TS-E 24mm f/3.5L
II, 1/20 s, f/18, ISO 100, +12 shift