SWEP help

There are 3 things i need help with on my SWEP. The lua cod would be most useful.

  1. How do i make it so when my SWEP is fired and hits an npc it disintegrates them and when it hits a prop/ragdoll it has no such effect?
    2.So it isn’t unaffected by the physics gun?
  2. How to add trails to the object when i shoot it? (My SWEP throws a ragdoll and I want a blue trail, I have tried the Util.SpriteTrail but i just get error message ‘bad argument #1 to ‘SpriteTrail’ (Entity expected, got nil)’

Even if you know the answer to just one of these please say. Any help would be much appreciated.