Since BSG refuses to re-work the skill system and gate keeps quests behind arbitrary skill leveling walls they have forced people to cheese skills (LVNDMARK spent half a damn stream cheesing SR for his Kappa) . Here is the easiest way to level your Stress Resistance.
-Walk into barbed wire until at least one of your legs are blacked out
-Jump until your SR is on cooldown (without taking pain killers)
-Wait 5 minutes, or extract
The easiest maps to do this on is: Reserve (run into barbed wire by sewer extract and then leave) or, Customs at ZB-012. Or if you are on any other map and find your legs get blacked out by a player or scav simply jump to max your SR before CMSing.
Notes: You will also level vitality from this, but it takes longer to max it out for that raid. It will also slowly level your health skill.