BBkiller's method works.

On a BB with a full keypad, you just press ALT + the letter.

On a BB with the smaller keypad (like the Pearl), you press ALT + the letter (if the letter is the first letter on the button), or ALT + the letter + the letter (if the letter is the second letter on the button).

For example, on the 7130k, there is a button that has both the letters J and K on them.

Pressing ALT + that key once = J
Pressing ALT + that key twice = K