API filter on multiple properties

I was thinking of was that the filter is not valid -- you cannot match only on values.  Well you can, but it is then detached from the property name and could match many properties.  You need to match on name and value together. 

filter=customProperties.name:PROPNAME,customProperties.value:PROPVALUE

The /device/groups idea is a good one if you are not matching on wildcards, like in this case (though you could use two passes to get an ID list, then iterate).  We have found the sometimes that is necessary due to lack of endpoints (e.g., there is no direct way to map a device datasource instance ID back to the datasource ID), but if you can use one query to do your work you should try to do so.