To delete multiple props is fairly easy.  First open the hierarchy editor.  Second Find a prop you want to delete.  Third drag all the rest of the props you want to delete to the first prop. Forth with the first prop as chosen in step 2 selected press the delete key and then make sure to check delete attached.  All selected props are then removed.

Or even easier (works in latest version of 12+) is to First open hierarchy editor. Second select first item. Third Control Select the rest of the items to delete.  Forth right click and choose Delete selected.  Fifth confirm your choice.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13