First you need to make a simple text file inside DOI files. The path should look something like this:
------\Steam\steamapps\common\dayofinfamy\doi\cfg
Name the file anything you want, for example you can name the file "Gore.cfg", basicly any name with ".cfg" at the end.

Open the CFG file you just created and write these commands:

Main Commands:

sv_cheats 1 - enables the cheats, some of the commands require them

cl_ragdoll_dismember_limb_limit 4 - the amount of limbs can be blown off at once ~tiny performance cost~

r_decals 9999 - the amount of live decals at one ~medium performance cost~

sv_ragdoll_cleanup 0 - disables the cleanup of ragdolls (the same character can have only 1 ragdoll in game by default) ~high performance cost~

sv_ragdoll_maxcount 500 - the max amount of ragdolls in game ~high performance cost~

cl_ragdoll_collide 1 - collision between ragdolls ~very high performance cost~

Additional Commands (commands that doesn't make the gore look any more great, but still worth mentioning):

cl_ragdoll_animation_time 10 the amount of seconds wiggly animation will play (after suiciding, falling down or getting killed by flame boy) ~small performance cost~

cl_ragdoll_dismember_bullets_fraction 0.1 - the amount of bullets you need to dismember a limb (example: 1 = one shot, 0.1 = 10 shots to dismember a limb) ~no performance cost~

Since I myself failed to make autoexec work, I decited to bind any key to run the cfg file instead. binding should look something like this:

• 1. Open console
  
• 2. Write: bind "<any key>" "<filename>.cfg"
  
• 3. That's it.

Best way to test if the bind works is to run any map in console ("map sicily liberation" for example), spawning in and just killing yourself for few times. If the bodies don't disappier, that means the config is working.

This whole guide was hugely inspired by him and his both reviews on Day Of Infamy's gore (especially by second one):
You're awsome lad, keep on making those great reviews!