Whatever mixture of fats you use in your pie crust, here’s a rule of thumb: keep it cold. Keep shortening in the freezer until you need it, and butter/lard in the fridge until you need it.
Trying to incorporate warm, soft fat into a pie crust will only result in chewy, tough pie crust. If you’re after a flaky crust, then you want to incorporate the fat as small, distinct chunks. If you want to get small, distinct chunks of fat, you’d best work with it cold.
Speaking of which, most recipes call for ice water. It’s not just a conspiracy of recipe writers to make your life more difficult. It’s just a variation on a theme. If you’ve gone to the trouble of selecting your fats, and keeping them cold, why on earth add warm water and cancel out all your efforts?
Just remember: keep it cold.