Suppose you want to set predefined values for your filters- you can always use the setFilterValue and getFilterValue methods, passing in the dataField of the column name that you wish to set the filterValue for. Also, see example 8, the first grid always loads up with default filter values. This is how its done:
//The first parameter is the dataField of the column of the filter you want to set the value on
//The second parameter is the value. The type of this object depends on the filter control that you are targeting. The type has to match its "setValue".
//The third parameter is basically a flag that tells the grid whether to run the filter instantly.
grid1.validateNow(); //Since we delay instantiate the Multi select, we need to do this for the
//grid to pickup that there is a filter in that value.