What “Bless up” means
Bless up wishes someone blessings. It works as a hello, a goodbye and a friendly thank-you, so you'll hear it at both ends of a conversation.
Examples
Bless up.
Blessings to you.
Bless up, mi bredda. Likkle more!
Blessings, my brother. See you later!
How to use it
Warm and positive, used between friends, in person and in messages. It suits almost any friendly situation but is a bit casual for formal settings.