I use heat packs for BPs if temps are under 70, and cool packs if temps are over 90, but I really prefer not to ship when temps are that high.
I personally prefer winter shipping, where I KNOW I need to keep them good and warm. Spring and Fall make me nervous, with their rising and falling temps, and summer can be problematic--I picture the animals sitting in air-conditioned areas with cold packs, and wince.