With the Component Editor, you can directly modify the values of individual skin point weights. Note that you can also paint these weights with the Paint Skin Weights Tool. If you want to set certain skin point weights to particular values, use the Component Editor. However, if you want to shape the deformation directly and are not concerned with specific values, use the Paint Skin Weights Tool (see Painting smooth skin point weights).
While you are editing skin point weights, you can reset the weights to their initial values at any time (see Reset skin point weights to default weights). You can also prevent indirect changes to skin point weights, which can happen if Maya is normalizing the weights (see Smooth skin weight normalization).