You can use any Pokemon that is able to learn Strength to push rocks.
strength
By using the move strength.
have it hold king's rock them trade it to another Pokemon platinum..
http://www.serebii.net/platinum/tornworld.shtml
you can get a rock climb TM (i forget where) and teach it to an able pokemon.
all the beginners can learn rock climb
use strength
from the foreign guy
dep
In Eterna Forest.
To catch garintina
The HM Rock climb is on route 217.