Make sure your IBM MQ Send Receive step has the 'Quiet' checkbox in the step info *unchecked*, and it will automatically extract all header properties and RFH2 properties into testExec properties.
The exact testExec property that each RFH2 property get stored in depends on its name and the RFH2 "folder" it appears in, but it should look something like 'lisa.ibmmq.Recv.Payload.Folders.usr.Props.property1'