In order to be able to cast while still moving, follow these steps:
1. While still outside of the dungeon, cyber up.
2. Without leaving mecha form, get on your mount (it will automatically take you out of mecha).
3. Wait for the CD of cyber up, and without leaving mount, cyber up again(will auto take you off mount once cybered)
4. Now enter the dungeon. This step is very important, if you don't enter a dungeon it won't work.
Tada, now just hold your move keys(preferrably one of the horizontal move keys) and oil bomb away. This'll work as long as you don't lose mecha form, or relog.