There's a few things you need to do and I couldn't have done it without the nice folks at the Modder's Workshop (Kweri, Sphalerite, trees, Hugo_the_dwarf, Kilroy the guard). Just thought I'd shoot some credit before I post the raws. There's two reactions, one to press meat into blood and one to brew blood into blood ale) There's quite a bit of copy pasting to do, so be ready!
First you need to throw these into the blood_template (in materials_template_default)
[MATERIAL_REACTION_PRODUCT:DRINK_MAT:LOCAL_CREATURE_MAT:BLOOD_ALE]
[REACTION_CLASS:BLOOD]
Then into the muscle_template (or whatever else you want to press to get the blood out) add this:
[MATERIAL_REACTION_PRODUCT:EXTRACT_BLOOD:LOCAL_CREATURE_MAT:BLOOD]
That will allow the reaction to take place with meat.
Into reaction_other, add :
[REACTION:PRESS_MEAT]
[NAME:press blood from meat]
[BUILDING:SCREW_PRESS:CUSTOM_T]
[REAGENT:meat:1:MEAT:NONE:NONE:NONE][HAS_MATERIAL_REACTION_PRODUCT:EXTRACT_BLOOD]
[DOES_NOT_DETERMINE_PRODUCT_AMOUNT]
[REAGENT:barrel:1:BARREL:NONE:NONE:NONE]
[EMPTY]
[PRESERVE_REAGENT]
[DOES_NOT_DETERMINE_PRODUCT_AMOUNT]
[PRODUCT:100:1:LIQUID_MISC:NONE:GET_MATERIAL_FROM_REAGENT:meat:EXTRACT_BLOOD]
[PRODUCT_TO_CONTAINER:barrel]
[SKILL:PRESSING]
[REACTION:BREW_BLOOD]
[NAME:brew blood ale]
[BUILDING:STILL:CUSTOM_R]
[REAGENT:blood:150:LIQUID_MISC:NONE:NONE:NONE]
[REACTION_CLASS:BLOOD]
[UNROTTEN]
[DOES_NOT_DETERMINE_PRODUCT_AMOUNT]
[REAGENT:blood container:1:BARREL:NONE:NONE:NONE]
[CONTAINS:blood]
[PRESERVE_REAGENT]
[DOES_NOT_DETERMINE_PRODUCT_AMOUNT]
[REAGENT:barrel/pot:1:NONE:NONE:NONE:NONE]
[EMPTY]
[FOOD_STORAGE_CONTAINER] barrel or any non-absorbing tool with FOOD_STORAGE
[PRESERVE_REAGENT]
[DOES_NOT_DETERMINE_PRODUCT_AMOUNT]
[PRODUCT:100:40:DRINK:NONE:GET_MATERIAL_FROM_REAGENT:blood:DRINK_MAT]
[PRODUCT_TO_CONTAINER:barrel/pot]
[PRODUCT_DIMENSION:150]
[SKILL:BREWING]
Into whatever creature you want to have brewable blood:
[USE_MATERIAL_TEMPLATE:BLOOD_ALE:CREATURE_ALCOHOL_TEMPLATE]
[STATE_NAME_ADJ:ALL_SOLID:frozen blood ale]
[STATE_NAME_ADJ:LIQUID:blood ale]
[STATE_NAME_ADJ:GAS:boiling blood ale]
Then add [PERMITTED_REACTION:BREW_BLOOD] and [PERMITTED_REACTION:PRESS_MEAT] to the dwarf entity.
There's a few things I'm messing with now so I'll update this when I'm done. Just FYI, the way it's set up, a 3 meat stack and a 300 meat stack will both create the same amount of booze. I had to do it this way because if the reaction creates more blood than would fit in the barrel, the blood ale will just go onto the ground.
I'll also update when I've got marrow beer and the rest of the delectable meat drinks I'm making.