Sculpting

I am struggling to sculpt my model, it started as a cube but now has a subsurface modifier on it, when I come to sculpt with it I find the faces don’t really change at all. Can someone explain how it works and maybe what I can do to make sculpting better? Thanks.

Use Multiresolution modifier for sculpting, not the subdivision surface modifier.

Before you add the modifier, manually subdivide the cube a few times, you don’t want to have a very low poly object as the base mesh. Then use the modifier to increase poly count and try with the different brushes. Make sure you have applied any scale to your object, and the brush strength is high enough

Then upload your blend file to http://www.pasteall.org/blend/ and tell us the link

Then watch tutorials.

http://www.pasteall.org/blend/25825 this is my model and the real problem is that no sculpting brush has any real effect

Do as Richard said, get rid of the subdivision modifier and use multiresolution instead.
You may want to apply the mirror modifier too.
On a different note, that basemesh’s topology is not good for sculpting. Ideally you want your quads in square shapes, not rectangular, and evenly distributed along your object.

Okay well i can’t do anything about the square faces unfortunately but I got rid of the subdivision modifier and am using the multiresolution one instead but the values won’t change so all three options are stuck n zero?

I suggest you apply your mirror modifier after getting rid of the Subdivision Surface one.

Sculpt mode is able to sculpt with X/Y/Z symmetry (look in the toolshelf panel to the right of the screen, you’ll see the symmetry option), you don’t need the mirror modifier that will only give you some trouble during sculpting.

Then once you have added a Multiresolution modifier, click on the “Subdivide” button located in the Modifier to increase the multires levels that you need and sculpt on them

You have to hit the subdivide button on the Multires modifier to add levels of detail. The buttons you are talking about will let you adjust according to how many times you hit the subdivide button. That way you can do large level sculpting at low detail and adjust upward as you add finer detail.