This is a huge topic.
Yes, baptism erases the stain of original sin, but it does not preclude our concupiscence (the propensity to committ sin).
I take it that you “get” this part.
Confession will absolve one with the right disposition of both mortal and veinal sins, however, it is not necessary for venial sins. I’m not sure that came out right…
Anyway, several things actually erase venial sins…again, one must be properly disposed. There is a saint who once said that all of us offend God at least 7 times per day…even unknowingly, and these are venial sins.
The use of Holy Water erases venial sins.Saying the “Our Father” is a prayer of deliverance and also absolves us of venial sins. The Mass itself begins with a prayer for deliverance and forgives venial sins.
If we are aware of an offense committed (like, say, you get a little snarky with someone) and you are sorry, say an Act of Contrition with sincerity and the venial sin is forgiven.
All of this is conditional upon the correct disposition.
I know there is more to this and many here can explain it so much better.