Should I be hitting with the side of my thumb, or the surface of it? (surface refering to the fleshy part directly opposite the fingernail)

Also, is it possible to slap on .9s? Because I'm having problems getting a sound.
I'm looking for a tab of The Marshall Plan, by Blue Oyster Cult, and of Mario Minor, by Powerglove. If you have one please PM me.
i believe youd slap with the side of your thumb. this being said only with experience in slap bass, im not completely sure.

and 9's wouldnt be very good for slapping id imagine, go for something thicker.
My Gear:
Gibson Faded Flying V
"Dante's Inferno" Iceman
Fender Hot Rod Deluxe 112

Quote by freedoms_stain
I can't imagine anything worse than shagging to Mark Knopfler.

Maybe shagging Mark Knopfler, but that's about it.
I use the side of my thumb. Never tried using the surface.

Yeah i'd go up a few gauges if you want it to sound good.