Filtering results after execution and multivalue parameter questions

Hi. 2 questions:

1.
I'm trying to execute a report, then allow the user filter the results using a value list from the report dataset in a dropdown list. When I create a filtering parameter, i can't figure out how to make it work on results after the report is executed.

2.
How can I make a multivalue parameter default to (Select All)?

thanks!
#1: You can simulate the "user-driven filtering" by using drillthrough actions to the report itself and setting the filter parameter accordingly. In any case, it will require the report to be reprocessed because filtering data may impact many other things (such as pagination).

#2: Make the valid values list and the default value both query-based and use
the same dataset column.

-- Robert