One of these pet brushes works pretty well getting them off the pet and they also take them off clothing. It helps if there's some pet hair already in it.
lookup burrpaw.com --its a little thing you run your hand in and then it adheres to all the hitchhikers and other seeds--got one last year--works pretty well. a lot better than picking all the dang things off.
Use the flat back of a plastic knife, or the edge of a plastic card like a credit card and you can scrape/push them all into a pile for much easier removal.