I use the Isp Decimator when tracking real hi gain type stuff, it's the best gate i've ever had. Liked it over the mxr smartgate, boss ns-2, and Rocktron hush. Its totally transparent, and really quiets everything down... very impressive.
i've never found a pre-tracking way to do this, that didn't effect my tone in a bad way...i usually record guitars in 4 or 8 measure sections, so each part gets the manual noise reduction once i get a good take (the noise reduction is also a way of leaving myelf a 'seal of approval' reminder...if i see any piece that got no noise reduction, it's an easy indicator that the piece needs to sound better :Spin: )