Weight painting (for particle control) with a linked object

Greetings,

I painted two weight maps (is that what they’re called?) on an object so I could control the dispersion of two different particle systems. When I link the object into my main scene (and create a proxy) the weight painted vertex groups are gone. I can’t weight paint a proxy. How do I then access my weight maps? Am I going about this wrong?

Thanks for the help,
MattVG