Transition From Up Dog to Down Dog
My suggestion for making this transition smoother is to try to involve your entire body in the process. Often the difficulty is due in large part to a mental block about rolling over the toes, usually related to a fear of crunching them in some way. If the rest of your body isn't working to take some of the pressure off of the toes, the transition can end up being laborious and even painful.
Next time you try it, see if you can use the strength of your arms pressing the floor away to help create the initial lift out of Urdhva Mukha Svanasana (Upward-Facing Dog). Then imagine your lower belly gently engaging and carrying your lower back and hips toward the ceiling. Finally, use the strength of your quadriceps drawing up to facilitate the roll over your toes.
If you can distribute the work of the transition this way, both mentally and physically, it will literally take some of the pressure off your toes. It will also direct your attention away from them. This can be useful when developing a new technique, since we often learn best when we direct our attention on intentions and actions related to the immediate goal, rather than overfocusing on the goal itself.