Have a look into the "doc" folder of your Softimage installation. There you should find a syflex folder which contains some Help-files. As far as I remember, there was mentioned something about weight maps.
Syflex has weightmap support for :
*point mass
*point stiffness
*nail strength
*pin strength
*mimic strength
and 2 weightmaps for the caches (still not sure what they are good for)
"Get Mass map" for example creates a weightmap and selects it so you can immediately paint on it using the weight brush.
When you're done, use "Set mass map".
If the object already has a Mass weight map, "Get Mass map" only selects it without creating a new one. You can paint more then and don't for get to re-apply using "set mass map" again.