I use HotKeyNet (www.hotkeynet.com) for my key broadcasting.
I use focus on my main and then my alts use:
/cast [target=focus-target] DPSSpell for DPS
/cast [target=focus-target-target] HealSpell for healing

That should get you started. You can adapt and learn as you go along. There is a lot to learn. Don't get discouraged, just practice and things will get better.