Repatriating chalk paint

[DueyCheatemAndHow]

Chalk painted a.chest of drawers years ago, it's now quite heavily marked. To refresh can I just recoat it or do I need to sand first?

RePAINTING! facepalm

Ooh I need to know about this as well.
I cannot remember but think I must have applied wax after the chalk paint because it’s gone yellow in places. Really looks tired and a bit manky. About to move house so I really need to refresh/ repaint but unsure how to tackle it. Any ideas?