I highly recommend what I call a butt spatula. It’s basically a little spatula that spreads any diaper cream onto baby’s butt without having to get it all over your fingers/under your nails. We have one for home & a travel size that goes in the diaper bag!

Baby Bum Brush, Original Diaper Rash Cream Applicator, Soft Flexible Silicone Brush, Unique Gift + Mini Diaper Rash Cream Applicator with Travel Case, [Blue + Gray] https://www.amazon.com/dp/B075VC9VNC/ref=cm_sw_r_cp_api_i_8JM7F8PPD59DG5X0QK8F