How do I make steel knife handles less slippery?

My butterfly knife handles feel a bit too slippery. They are made of stainless steel. (knife is Bradley Kimura VI )

I tried washing my hands with strong soap (so that my hands aren’t oily or greasy), but that only works for a short while.

Would cleaning the handles with alcohol or something else work? I basically need something to make the handles less slippery without ruining it or altering it (sanding, taping, etc is NOT an option)

Also, while I’m at it: how would I go about cleaning the knife (maintaining it so it doesn’t get crummy) ? Do I need to use stuff like WD40 ?

Sorry if this is a dumb question (I just want to make sure I don’t ruin my “fancy” new knife).

Thanks in advance!