I've used Russ's formula before and have had sucess with it. Just a
few things that I've observed with spalting, no matter what method you
choose - 1) it works better in warm or slighty hotter weather (Living
in Las Vegas is great for this!), 2) If using a container (like a trash
barrel), make sure to cover it up and keep it 'out of sight', so that
animals or small children aren't tempted to play around with it. 3)
Moisture is probably the biggest part in the process (If you add too
much water to the mix, don't worry about it!)

As far as determining what external signes to spot, mushrooms are
really good, white moss/slime is good too. How long you want to spalt
is up to you, but I check it every three months or so by pulling out a
log (with gloves on), and cutting a portion of it off.

As stated before, some species of wood just don't spalt very well/at
all, and some only get moderate results.