I and countless other cyclists rarely if ever have a problem getting motorists to notice our hand signals. If fact, about half the time a hand signal is not required at all, because just looking back (not a quick glance, a real look) causes them to notice and slow down.

Now, a hand signal does not give you the right to move or turn laterally. If someone else has the right of way, you have to wait for them to go by, or until they yield to you. I say this because many cyclists seem to think that to turn all they have to do is signal and go.

In you case you were slowing to turn right, and the car behind you hit you? Well, the other thing you might want to get is a mirror...