edit: i should start by saying I use this method most of the time... i realize this post made it sound like i was not recommending downshifting to slow down. this is not the case....
Tagging on to what crossroads said, I'd advise that you should rev-match by blipping the throttle to minimize the jerking effect of going down a gear.
More importantly, keep in mind that these big twins have a LOT of engine braking, and can break the rear tire loose on dirty pavement (or worse, gravel). Various conditions can be a poor choice for downshifting to slow down (even when rev-matching).
use good judgement- if you are on a low-traction surface, use your brakes evenly to slow down. Low traction surfaces can be many things in this case: rain, gravel, light sand on surface, GOING DOWNHILL, etc.
be smart, and keep the shiny side up!
2011 Victory Kingpin 8-Ball
Tach / Dual front discs with Vesrah JL pads / Penske shock / S&S Intake / PCV & autotune / RPW Thor exhaust with homemade custom baffle / Tsukayu leather "Strong" bags / Avon Cobra *Radials* / Ness Vegas Peg Conversion / Ness Vegas driver's seat / Custom T-Apes from BR Custom Cycles