I make plunge cuts as follows:
- Tilt the saw forwards to that the front edge of the baseplate (aka "shoe" is resting on the work piece. The back edge of the baseplate is elevated so the blade and blade guard are held clear of the workpiece.
- Align the notch in the baseplate with the cut line and square the front edge of the baseplate with the cut line. Not that the front edge of the baseplate is at right angles to the saw blade, so if this is square to the cut line, the saw blade will enter parallel to the cut line.
- Keeping the front edge of the baseplate in contact with the workpiece, use one hand to raise the blade guard and hold it in a raised position.
- With the saw still off, slowly lower the blade to make contact with the workpiece and make any fine adjustment to the angle of the cut.
- Raise the blade slightly, again keeping the front edge of the baseplate in contact with the workpiece, and still holding the blade guard in a raised position, engage the saw and lower the blade to make the plunge cut.
- When the baseplate of the saw is in full contact with the workpiece, you can release the blade guard and continue sawing as normal.
The point of all this is that the front edge of the baseplate keeps the saw steady and aligned with the cut line, and provides a pivot that the saw can rotate around as it makes the plunge. This makes it possible to make the plunge portion of the cut one-handed.
I learned this technique and several others from this video: Skil Saw Pro Tips
Regarding safety, this is for sure not a method that will be found in the manual. I'm not sure I can speak to all the ways this might go wrong. Kickback is the obvious one - I'm careful to keep my body out from behind the saw so that if there is a kickback it won't be coming towards me. Obviously a well supported and secured workpieces is key to safety too.