Slide from 4 to 2, I pluck both times right? I'm pretty sure I do but I haven't read specifically to pluck 2 times or just let the second note ring.

ive never heard of anyone plucking on the end note,
pluck the 4th, slide down to 2, then just let it ring or whatever.....
No, don't listen to Travlembo, you pluck once and move your finger (fully pressed) to the indicated fret. Period.
Live Rig:
Ibanez Rg 150R w/ Duncan 59s
Marshall JCM2000 TSL60 Head
Mark IV Combo
Marshall 1960a Cab w/ Vintage 30s
Ibanez RG1570 Prestige w/ Duncan 59s
Jackson SLSMG Soloist
Currently in Ontario, Canada.