First, you need to understand that the only way to increase a happy ghast's flying speed in Minecraft is through commands. The creature is not affected by any swiftness potion thrown at it.

However, there is a simple trick to spawn the ghastling without the dried ghast block using commands in Minecraft Java Edition.

Players interested in automating their commands in Minecraft will have to use Command Blocks, but they’ll need to update their settings to add them into the game.