everything that karset22 said about the kiting aspect, is right on. IMO, its great to play solo, so you know how to kite zeds, especially husks and FP's. Scrakes are easy to kite, but you have to put yourself in a tactical advantage spot because when they rage, they will easily outrun you, so you better be ready to bring the heat. A small tip for scrakes, would be that if one of them catches up to you and "sticks" you, its best to stay still and let him dig in, while your pumping his face with lead. When the saw is in you, its doing a steady amount of damage, and doesn't spike at all. If you attempt to escape from the scrake's grab, then he'll run and slash you before goring you. His slash does a high amount of damage, so its best to just take it, while killing him.
As for loadouts, if your trying to better yourself with the medic guns, then its worth using the MP5 and MP7, so that way you can have infinite healing darts, and you can easily practice on your aim with them. For me as a level 6 (and even hen i was a level 5), my personal load out would be katana/MP5/LAR. MP5 is just a great medic gun to have, LAR is great for 1-bodyshot killing crawlers and for taking out things that are far away, and the katana is great for the times when the sh!t hits the fan and need to kite, or when your out of ammo. I have seen a few medics using the nade launchers (I forget their names, I think its a M79 and M32?) but usually its only useful for open maps or maps where you can stand above the zeds.
Now, my tips being a better medic are pretty simple. First tip, if theres a chance to heal someone else, heal them. Being a medic is great because your medic needle recharges so fast that its possible to heal yourself and then run over to a friend, and heal them. Second tip, if theirs even a slight break from combat, heal yourself. Tip three, if things get out of control, attempt to heal everyone you can, especially anyone with low health. IMO, when things are getting out of hand for me, I use the medic gun to heal those who are farthest away (regardless to how hurt they are) and use the medic syringe for anyone thats really close by. However, while Im doing this, I make my way closer to whoever is hurt the most, so that way I can then reach them with the syringe. Tip four, if you and someone else are the only ones alive, then whatever you do, make sure you heal them. Besides, if its just you and him, your going to be in for a long round if he isn't alive, and if you die, then its not going to matter too much especially is he isnt a medic or beserker. Tip five, although its good to do this for most difficulty settings, it is HIGHLY recommended that you tank a raging FP on difficulties that are above Hard. Being a high level medic, you can easily take a beating without dying as fast as the other people. Tip 6, if you or someone else is on fire, one shot from the medical syringe can prevent any more burning damage (health damage that is, I don't think it stops armor burning)
And finally, basic tips for kiting. Like Karsey said, you have to know the map in order to plan your kiting path. If you use the katana like I do as medic, then when you running around, its best to make sure that there isn't any zeds in the path that your heading to. If the path is clear, then its best to stick near the corners and pick of so of the small zeds. With my load out MP5/Katana/LAR, its best to use katana for clots, gorefasts, and stalkers, use the 9mm for bloats, and use the LAR and MP5 for husks, crawlers, and sirens. Once your able to get these baddies gone, you can kite the FP by attacking it in 2 second intervals. Due to its raging mechanics, its possible to kill it without it raging. Just make sure you don't do too much damage at once, or stay in its Field of Vision for about 12 - 15 seconds. The biggest threat you would have to deal with as a medic, would be scrakes and clots. Clot's magnet hands can make it easy to panic, where as the scrake can make things difficult because the medic lacks offensive weapon buffs.
