W. Watson wrote:
In general how
does one use these ideas to his advantage when paddling? For example, is
there a paddling tactic that one should employ when noting that one is
about to enter slower moving water, and vice versa? As another example,
what tactic should be used when approaching boiling water? Maybe these
circumstances are handled by some general paddling strokes.

It's all a matter of degrees and direction. If you're going with the
flow and you paddle into a wider area where the current slows, so do
you, but the difference in speed doesn't create any problems. The same
is true going from slow to fast water. It's not like you're getting
slammed around, just gradually accelerating or decelerating. It's
different if you're entering an eddy from a fast flowing current or
vice-versa, but that's not the question you posed.

As for boiling water, it depends on how much boiling is going on. In
water where the upwelling just makes a relatively flat "footprint", it's
no big deal. If you enter off-center, it will push you slightly toward
the outside of the boiling area, but that's pretty much all you'll feel.
Standing waves could be considered as large boiling water, but they
require an entirely different set of skills.