We've always used one with all our whippers. Chasing is what they are born to do, after all :) I'd highly recommend the larger ones like what you get for horses at a farm store. I think they are called lunge whips.
https://www.amazon.com/dp/B07K81SBLT/ref=cm_sw_r_cp_apa_fab_q6CDFbMPCVRC7