Blaziken can learn Sand Attack, but this move only lowers the accuracy of the target.
I've never played Pixelmon myself, but if there is TMs, Blaziken can be taught the following Ground Type moves:
•TM26 Earthquake, Physical (Power-100, Accuracy-100)
•TM28 Dig, Physical (Power-80, Accuracy-100)
•TM78 Bulldoze, Physical (Power-60, Accuracy-100)
As far as I know, Blaziken cannot learn any Dragon Type moves.
Blaziken can learn these Rock Type moves though:
•TM39 Rock Tomb, Physical (Power-60, Accuracy-95)
•TM71 Stone Edge, Physical (Power-100, Accuracy-80)
•TM80 Rock Slide, Physical (Power-75, Accuracy-90)
If your friend is a Ghost Type Gym Leader, you could catch a Hoondoom, which is a Dark/Fire Type. Dark Types are super effective against Ghost Types. I don't know if you can, but the Litwick evolution chain is full of Fire/Ghost Types. Ghost types are super effective against Ghost types as well. Blaziken being a Fighting type cannot be hit by Ghost attacks anyway.
Hope this helps,