Its a little clumsy but you can use the character viewer in the Apple system preferences under keyboard preferences select keyboard and character viewer. Then there will be a little symbol with a dropdown special character selector that includes a number of bullet points. Then after you insert the first one you can use copy and paste to place in as many cells as you like quickly.
The only way I can think of to make the text wrap properly is to right justify it., or place the special bullet point in a very narrow column.