How do you use a surface marker buoy?
Open the bottom of the surface marker buoy and hold it above your regulator exhaust valve (where the bubbles come out when you exhale). Breathe out a few times until the buoy partially inflates and tugs upwards on your hands, but avoid adding so much air that you cannot maintain buoyancy.
How do you inflate SMB?
An SMB with a tube thats open on the bottom can be inflated by adding air from the second-stage regulator (or octopus regulator) into the tube. Simply invert the regulator beneath the open tube and depress the regulator purge button briefly.