Open the image and create a copy, use the Duplicate Layer command ("Duplicate layer") from the menu Layer ("Layer"). All changes need to make on a new layer so as not to damage the main image.
On the toolbar, select the Brush Tool (Brush) and set its parameters in the properties panel: size 3 px, hardness 100. Press P to activate Pen Tool (the Pen). It will have the properties you defined for the brush.
To smoothly bend straight segments, use the Direct Selection Tool ("Arrow"). It can be activated by pressing the A key in the English layout. With the arrow of white color changes the selected polygon. The black arrow moves the selection.
Passes through this point cut a tangent, which you can use to change the shape and length of the stretch of the selection. To do this, grab the mouse end of the control cut and pull. Give the selection of the desired bend. To remove an anchor point, click the right button and select the Delete Anchor Point.
When you gently turn the object, click within the selection right click and select Make Selection ("Create selection"). In the new window set the Feather Radius value ("feather Radius"). The higher the value, the more blurry the edges of the selection.
Create and delete control points by using tools from the group P. They look like "Pen" with the signs "+" and "-"