OKAY. I got them working properly.
First, add [MATERIAL_REACTION_PRODUCT:FUR_MAT:LOCAL_CREATURE_MAT:FUR] to SKIN_TEMPLATE in material_template_default.txt.
Now add [ADD_MATERIAL:FUR:TANNED_FUR_TEMPLATE] to the bottom of [BODY_DETAIL_PLAN:STANDARD_MATERIALS] in b_detail_plan_default.
Next, add the following to either material_template_default.txt or a new material_template file if you want to keep them seperate.
[MATERIAL_TEMPLATE:TANNED_FUR_TEMPLATE]
[STATE_COLOR:ALL_SOLID:BROWN]
[STATE_NAME:ALL_SOLID:fur]
[STATE_ADJ:ALL_SOLID:furs]
[STATE_COLOR:LIQUID:BROWN]
[STATE_NAME:LIQUID:n/a]
[STATE_ADJ:LIQUID:n/a]
[STATE_COLOR:GAS:BROWN]
[STATE_NAME:GAS:n/a]
[STATE_ADJ:GAS:n/a]
[DISPLAY_COLOR:6:0:0]
[MATERIAL_VALUE:2]
[SPEC_HEAT:420]
[IGNITE_POINT:6508]
[MELTING_POINT:NONE]
[BOILING_POINT:NONE]
[HEATDAM_POINT:750]
[COLDDAM_POINT:18900]
[MAT_FIXED_TEMP:NONE]
[SOLID_DENSITY:400]
[LIQUID_DENSITY:NONE]
[MOLAR_MASS:NONE]
[IMPACT_YIELD:10000]
[IMPACT_FRACTURE:10000]
[IMPACT_ELASTICITY:50000]
[COMPRESSIVE_YIELD:10000]
[COMPRESSIVE_FRACTURE:10000]
[COMPRESSIVE_ELASTICITY:50000]
[TENSILE_YIELD:10000]
[TENSILE_FRACTURE:10000]
[TENSILE_ELASTICITY:50000]
[TORSION_YIELD:10000]
[TORSION_FRACTURE:10000]
[TORSION_ELASTICITY:50000]
[SHEAR_YIELD:25000]
[SHEAR_FRACTURE:25000]
[SHEAR_ELASTICITY:50000]
[BENDING_YIELD:10000]
[BENDING_FRACTURE:10000]
[BENDING_ELASTICITY:50000]
[MAX_EDGE:0]
[ABSORPTION:80]
[IMPLIES_ANIMAL_KILL]
[LEATHER]
[ITEMS_LEATHER]
Now create a new reaction file, and paste in:
reaction_<whateveryoucallthefile>
[OBJECT:REACTION]
[REACTION:PRODUCE_LEATHER_BEDDING]
[NAME:create leather bedding]
[BUILDING:FURRIER:NONE]
[REAGENT:A:1:SKIN_TANNED:NONE:NONE:NONE]
[PRODUCT:100:1:BED:NONE:GET_MATERIAL_FROM_REAGENT:A:NONE]
[PRODUCT_DIMENSION:150]
[SKILL:LEATHERWORK]
[REACTION:TAN_A_FUR]
[NAME:tan a fur]
[BUILDING:FURRIER:NONE]
[REAGENT:A:1:NONE:NONE:NONE:NONE][USE_BODY_COMPONENT][UNROTTEN]
[HAS_MATERIAL_REACTION_PRODUCT:FUR_MAT]
[PRODUCT:100:1:SKIN_TANNED:NONE:GET_MATERIAL_FROM_REAGENT:A:FUR_MAT]
[SKILL:TANNER]
[AUTOMATIC]
Lastly, create a new building file and paste in the following:
building_<whateveryoucallthefile>
[OBJECT:BUILDING]
[BUILDING_WORKSHOP:FURRIER]
[NAME:Furrier's Shop]
[NAME_COLOR:7:0:1]
[DIM:3:3]
[WORK_LOCATION:2:2]
[BUILD_LABOR:TANNER]
[BUILD_KEY:CUSTOM_SHIFT_F]
[BLOCK:1:0:0:0]
[BLOCK:2:0:0:0]
[BLOCK:3:0:0:0]
[TILE:0:1:' ':' ':150]
[TILE:0:2:' ':' ':'/']
[TILE:0:3:'-':' ':' ']
[COLOR:0:1:0:0:0:0:0:0:6:0:0]
[COLOR:0:2:0:0:0:0:0:0:6:0:0]
[COLOR:0:3:6:0:0:0:0:0:0:0:0]
[TILE:1:1:' ':' ':'=']
[TILE:1:2:'-':' ':8]
[TILE:1:3:' ':' ':150]
[COLOR:1:1:0:0:0:0:0:0:6:0:0]
[COLOR:1:2:6:0:0:0:0:0:6:0:0]
[COLOR:1:3:0:0:0:0:0:0:6:0:0]
[TILE:2:1:'-':' ':8]
[TILE:2:2:' ':' ':8]
[TILE:2:3:' ':150:' ']
[COLOR:2:1:6:0:0:0:0:0:6:0:0]
[COLOR:2:2:0:0:0:0:0:0:6:0:0]
[COLOR:2:3:0:0:0:6:0:0:0:0:0]
[TILE:3:1:150:' ':8]
[TILE:3:2:' ':' ':8]
[TILE:3:3:' ':240:' ']
[COLOR:3:1:6:0:0:0:0:0:6:7:0]
[COLOR:3:2:0:0:0:0:0:0:6:7:0]
[COLOR:3:3:0:0:0:7:0:1:0:0:0]
[BUILD_ITEM:1:NONE:NONE:NONE:NONE][BUILDMAT][WORTHLESS_STONE_ONLY][CAN_USE_ARTIFACT]
You should now be able to tan skin at the Furrier's Shop for fur, which can then be used to make leather goods at the Leatherworker's shop or turned into bedding at the Furrier's shop.