How to get baby to self soothe?

Kate🔅 • FTM ⭐️
Hello. I'm sure this has been asked and answered, but I couldn't find a thread.
Anywho....
My 5 month old has gone from sleeping 3-4hrs at a time, to 30 min. Seriously. He wakes up during the night several times. I've read of the 4 month regression and believe I'm dealing with that. He won't stop crying until I pick him up, if I don't do it quick enough he gets hysterical.
My mom said to just let him cry himself back to sleep, I'm not very good with doing that.
What has worked for you?