You won't use the notation to get a sound, is more to have a visual of the score.
The "sound" of a dead note you get it from the instrument, if you have a palm mute sampler you trigger that in the instrument, selecting the right patch or you trigger that using whatever method the instrument has implemented (usually a modifier or key-switch)
For that the old Event View or nowadays PRV are much more efficient than Staff View.
in normal midi playback you'll get more close to a dead note using a note length of 1 or 0 rather than velocity=1, but it depends on the samples and configuration of the instrument really. Trial and error.
But I'll tweak that on PRV hands down, not on "notation"
dd