Simply Maya User Community - View Single Post - apply shader to all object instances

this might be a simple task but I didn´t find any working solution yet - please help!

task: select lots of objects and all their instances via script. then apply a shader.

what I have so far:

Code:

if (objExists("geo_test" + "*"))
    {
    select -hi ("geo_test" + "*");      
    string $sel[] = `ls -sl -ap`;
        for ($item in $sel)
            {
            sets -e -forceElement testSG;
            }
    select -cl  ;
    };

unfortunately I can´t figure out how to select all the instances too. only the parents get shaded :/