This will work for Heal Thy Self and Playing Doctor.
What you will need:
2 Survivors.
Whole lot of plague cure; This is probably the longest part of this solution however as you progress through Heartland and save some plague samples, you should also have your community up to a point of being very sufficient to create a lot more plague cures with the samples you have just by playing the game. If you need more, use the CLEO relay to summon Zombies or just go out and kill some. I found every 3 or so dropped a plague sample; you can also look for med supplies to create bulks of the good stuff.
Hiking, large or army issued back packs to carry more cure.
On the purpose of testing this out, both of my survivors had a total of 10 plague cure each. Now as you can carry 5 per slot on Heartland, I encourage you to use a lot more as it will make this way faster.
This is all you will need. Please only use the standard plague cure. Enhanced plague cures will not work.
You will NOT need to do this co-op, can be done in single player.
You WILL need to delete local saves; just be careful to not delete everywhere and lose everything.
You WILL need at least 20 plague cures minimum to do this in quick time.
Where to go?
I suggest the final wall to grind this achievement, why? there's a plague wall near by and all you will need to do is run into it and give yourself the plague. There also seems to be zero zombies to give you hassle. IF there's any about, feel free to shoot or bash their heads in.
Method
I would suggest grinding this after you beat heartland once. As when you do, you will have the option to continue and it will bring you back to the final wall anyway and there shouldn't be any zombies around. IF there are, then bring some plague busters to rid them. Juggernauts, and other freaks shouldn't appear unless you damage the wall. AVOID damaging the wall as this will bring you a heap of problems.
Now, once you have 2 survivors, stock both with 10+ plague cures each, completely exit the game. Hit the home button and press start on state of decay 2 and hit quit. This will create a cloud save. Start the game up again and hit continue on heartland and it should bring you back to the final wall with your 2 survivors with all your items.
what you should now do is switch to a survivor who doesn't have blood plague and run into the goo near the plague wall. Now that they are infected, switch over to the other survivor to administer the cure. Whilst the other survivor is injecting themselves, you can now run into the goo and infect yourself. Once infected, switch to the now cured survivor and have them, administer the cure to you. Rinse and repeat until both survivors run out plague cure.
What you will now need to do, if you haven't got the achievement is hit the home button, select state of decay 2 and manage & add-ons and find your saves. Delete your save file from your Xbox. DO NOT DELETE EVERYWHERE and also remove the reserved space (just in case)
This will now stop the game, now load up your game again and allow your Xbox to sync data for State of Decay 2. Once you have loaded up the front screen again, select heartland and hit continue. This will now bring you back to the final wall with your 2 survivors and all items replenished. Then feel free to rinse and repeat until you have earned the achievement.
For HEAL THY SELF,
Just do the same but with all the plague cures on one survivor, continuously run into the goo and infect your self and hit RB to administer the cure to you survivor. Once you have ran out follow the paragraphs above in bold
Thanks to Darth Stigious and Radiant Synergy. For their guides on this game; as it helped me with finding this solution and making the achievement a whole lot less of a grind, as I was able to get both achievements within a couple hours (at most) Most of this time was testing some stuff out and you should be able to get this a lot quicker if you bring more plague cures.