Fig 1. Sculpt Menu

Fig 1 shows you what you get when you use the <4> or <5> keys:

<4> - Push 

Press and hold the <4> key to push in the surface at the mouse pointer location.

<5> - Pull 

Press and hold the <5> key to pull out the surface at the mouse pointer location.

<G> - Sculpt Marked 

Fig 2. Sculpt Marked

You can use <5><G> to pull a marked area out, or <4><G> to push it in. First you will be asked for a Border value; this is the area outside of the marked faces that is used to blend in the sculpted amount (see left side of Fig 2). Next you'll be prompted for the sculpt amount itself, and then finally the affected area will be shaded blue and you are asked to confirm with a <Y> key if the modification should proceed. Type <N> if you want to abort at this point.

<Shift-G> - Sculpt Marked Inwards 

If you only want the marked faces modified, then use <4><Shift-G> to push or <5><Shift-G> to pull. You are prompted for the sculpt amount, and straight after that the surface is modified. The sculpt amount is blended across all of the marked faces, with zero at the boundary and the maximum amount towards the center (see right side of Fig 2).

Fig 3. Settings

[edit] Additional Settings

If you click on the gray Sculpt button in the Brushes panel, then some additional settings are shown (see Fig 3). Click on the Sculpt button again to hide these away.

Shape 

Fig 4. Shape

Sets the shape of the push and pull brushes (see Fig 4).

Dir 

Sets a special direction for the push or pull action.

Off 

No special direction. All points are moved in the direction of the average surface normal at the mouse pointer location, and this is good for most sculpting work.

Eye 

All points are moved directly towards or away from the eye/viewer.

Out 

Each individual point is moved in the direction of the surface normal at that point.