On my husband, it took my middle finger being all the way inside (which he liked) to feel the rough, swollen p-spot (which he REALLY liked). I'm still learning how to do this but that was enough encouragement for me to feel confident to continue exploring.
And I second the idea of a toy. Even though you can't feel what's going on inside, it might make it easier to feel confident with the penetration versus fiddling around with a finger. And they do hit a lot more area than just a finger.
Now I know how those teenage guys must have felt back in my high school, but this time *I* am the fingering noob.