Question about high heel shoes

Hello fashionistas.
I have a weird question about slippery high heel shoes.
I have learned to walk in heels up to about four inches, as long as the
shoe is more of a boot style, or one that grips my foot all the way
around.
What I can't seem to master are heels that are either slippery inside,
so my foot is sliding all around, or ones that are mule style, with
nothing to help hold the foot in place.
Is there some trick to this I need to learn? Is there something I can
put in / spray on the shoes to help with grip?
I have use a heel grip (when the style can take it) because my left
foot is about a half size smaller than my right, so that foot is always
problematic. Sometimes, though, I can't keep my feet in the shoes, even
with the grip. I'm walking like I've got mental problems because every
step I take my shoe comes off my foot! <grin/ roll eyes>
So how did any of you learn to walk in heels?
Thanks in advance for your advice.
Tetonia