there are 2 main types of medic xp theres the "healing" xp and the crafting.
The trick to getting fast crafting xp is easy just grind bio controls in practice mode and then when you can make advanced bio controls make those in practice mode. This process can be afk macroed if you want to cheat

note your going to need atleast 5 food crafting kits to craft constantly without stopping
To get healing xp for the medic line your gonna need a master doc friend who has warcry and health and action buffs (no secoundarys) and some heavy armor for your doc friend to wear and good stim B's. why use warcry vs tumblers? warcry makes a person lose HAMs 3-4 times faster then someone tumbling. so get a thug mission(something with a base that wont attack back) and head to that base with your doc/warcry firend. kill whatever npc's guarding the nest and position your master doc about 8-10m away from the nest (so that he cant accdently hit the nest). then have your doc friend start warcrying. you can also use your doc friends to teach you all the medic line things.
so you made master medic at last not much will change for the doc or cm grind. A cm could get more friends to warcry the base and use area stims or just use the stim B's or C;s or D's whatever you have. a doc can use the same process.
to get crafting xp the fastest way is still advanced bios in practice mode