Boosting
When there is a lot of horizontal distance to cover on a relatively flat surface, this is optimal. This includes most "access tunnels". To optimize boosting you should know that by holding the stick towards the direction you are going the game will try to slow you down to normal rolling speed. This means that after 1 or 2 boosts you should let go of the stick to reach higher speeds. This is especially important in long Morph Ball tunnels such as South Quarantine Tunnel. Here's an example of "Access Tunnel" type room movement: