When in doubt, ask. I’ve also very gently and slowly tested the waters so to speak in the heat of the moment and judged body language, and confirmed that they are cool with this in the moment. Some girls will gently move your hand away when you touch them on the outside, some are cool with outside touching, and others are cool with digital penetration. Some will grab your hand and push fingers in. But everyone is different. Should go without saying but these are critical points re fingers and pussies.
1. Cut your fucking nails, you caveman. And make sure you done leave any sharp edges.
2. make sure your hands are CLEAN. If you have a manual job that makes your hands regularly dirty looking, use the best cleanup wash you have. Sometimes working with your hands leaves them rough and gnarly. That may be too much for some girls alone. Good plan to moisturize your hands regularly.
3. Forget the term “finger banging”. It should be banished from the lexicon. You should never “bang” a girl’s vagina with fingers. This is a porn invention. Gentle is best and if she wants more intense stimulation she will let you know.
While “petting” is taught to us as “less” than intercourse, fingers can be harsher on vaginas and asses than a penis. Just go slow, ask, make sure she is cool, and don’t be a dick if she’s not at all into FIV, or asks you to stop/ back off. There are tons of other fun things to do with cocks, pussies, mouths , boobs, hands and asses to keep everyone happy. Just imagine if your cock had long dirty nails growing out of the end of it, or looked like it had bathed for a year in used 10w30.