Are you a fan of the aquatic? We are too. May has many advantages on Cross|Up that surpass your typical fight stick or pad. Today we are focusing on charge motions in Guilty Gear -STRIVE-. Particularly dolphins.
The extra buttons in the layout with the white rim - those represent Left / Down / Right and the button at the bottom is Up.
HORIZONTAL CHARGE
Using the extra buttons, our right hand can easily finish the motion for us. Charge Down-Back with the joystick, let go of the stick and press forward with Slash (or HS).
VERTICAL CHARGE
Charge Down-Back with the joystick, then press the Up button with your Thumb on the right hand.
This works because when you input a vertical Cross|SOCD (X|SOCD), the Up direction will always out-prioritize Down.
Most of your Vertical Charges in a GGST match come from a blocking Down-Back position, which is fine. A perfect Up direction is not required to finish. The Down-Back becomes an Up-Back to finish the motion. 
Mr. Dolphin is set free.
If you have any questions about Guilty Gear -STRIVE- on Cross|Up, please join our community on Discord and visit the #airdash-fighters channel. In addition, be sure explore the "Cross|Up" and "GGST" tags at the bottom of the post and visit our Cross|Up Index for more How-To content.