Mashing Text

Most text in this game can be mashed forward with any button, including the D-pad (up/down/left/right). As such an effective way of advancing text is to spin your thumb around the D-pad.

Leaving the Shop

Since the D-pad advances text, you can mash left/right, without worrying about A or B triggering other shop text boxes. When  you reach Dr. Light's prompt (and you can therefore use B to leave the shop), items will start scrolling since you are already pushing left/right.

When you see items move, Press B. advance text with left/right, then press A to confirm.