I can think of a couple of things that may help your new healers out.
~ It is not just the new healer's job to learn how to play up to the rest of the group’s level. What the rest of the group has to do is go out and get a couple of stacks of medkits and some stims that will help them stay up for a little longer. Yes this is you too DPS, I know that +dmg stim makes you look awesome but if your dead you can’t do any dps. Allowing the healer to get good at keeping the tank up is the first step then they can branch out to get everyone else.
~ If there are multiple healers in the group then there are multiple roles of healing in each group. The main healer and the off healer. The main healer’s job is the tank; they are not to look at anyone else’s health bar but his/hers. The off healer gets everyone else. These roles can be decided by who has HoTs, AoE, and who has direct heals. Hots and Aoe will be the off healer and direct will be main healer. The off healer can also throw up some Hots on the tank if they are having some trouble.
~ You picked to be a healer, that is your job. One of your first steps when you are new is to remove your damage spells and attacks off of your bar. You have a group of Dps there and that is their job, trust in them.
~ You have to be aware of your surroundings also. I know as a healer you can get blinders looking at the little health bars, but you need to pay attention to what is happening around you too.
~ How I heal is set my heals to my hot bar starting at 1, I use my mouse to pick who needs heals and press the button I want, rinse and repeat. Some people prefer to use f1 keys to choose their targets. It is your preference.
~ Lastly this is not for everyone but it helped me. PVP I found that playing PVP and watching what was going on I could get a good idea of who needs what kind of heals. Tanky types bar moves a lot slower in 10 hits that a squishy in 1. Learn how to heal proactively as you can instead of retroactively and sometimes too late.
Hope this helped you out