[SECRETION:LOCAL_CREATURE_MAT:FLUID:LIQUID:BY_CATEGORY:ALL:SKIN]
now to explain it so you know what goes where:
[SECRETION:A:B:C]
A: material, this can be 1 to 3 sections long (MUD, LOCAL_CREATURE_MAT/INORGANIC:material/inorganic(like gabbro), or CREATURE/PLANT_MAT:creature/plant:material)
B: Material state (SOLID, LIQUID, GAS) what state the material is secreted as (INORGANIC:NONE:LIQUID will have it secrete magma on the defined tissue, coming up next)
C: bodypart and tissue to secrete the material. So you choose a selector type (BY_TOKEN:RH:SKIN, BY_TYPE:GRASP:SKIN, BY_CATEGORY:HAND:SKIN) I included a bodypart target too which is Hand(s) so RH is the right hand token (so only secrete material from the skin of the right hand) GRASP means secrete material from all GRASPING body parts and HAND means secrete material from all bodyparts categorized as HAND. Now there is also the end part SKIN that is the tissue layer on the bodypart, most limbs and external parts will have SKIN or SCALE (HAIR too) but internal organs mostly have their own named tissues EYE, BRAIN, LIVER so lets say I wanted Eyes to ooze solid salt (sounds really painful) I'd use one of these two methods ([SECRETION:SALT:SOLID:BY_TYPE:SIGHT:EYE] or [SECRETION:SALT:SOLID:BY_CATEGORY:EYE:EYE])
Also for states you can try these SOLID, LIQUID, GAS, POWDER/SOLID_POWDER, PASTE/SOLID_PASTE, PRESSED/SOLID_PRESSED
paste and pressed might not work but I know 100% that SOLID, LIQUID and GAS work. I'm certain that POWDER/SOLID_POWDER could work too but I don't remember if I've tried that yet.
EDIT:
NOTE --- Secretions do not work in ARENA MODE only in real gameplay.