I recently removed some white wooden baseboards (drywall) to install
flooring. For re-installation, I need to 'finish' the edge between
baseboard and wall. Previously, some form of caulk achieved this...but
it made the removal of the baseboards difficult (paint peeling, drywall
paper tearing, etc.). In addition, the top of the baseboards were
really difficult to keep clean..grime seemed to accumulate there, and
removing the grime seemed next to impossible.

For the re-installation, I'm looking a smooth, straight line between
baseboard and wall, but I would like to avoid the problems mentioned
above (dirty, difficult to remove baseboards after the fact). Any
suggestions on how to achieve this? What type of filler/material
should I use as interface between wall/baseboard? Lightweight
spackling? Some special type of caulk?

What about method of application? What's the best way to get a smooth,
straight line?

Cheers,
Dave