There is only a small number of tokens that can be added (or removed) through CE_ADD_TAG (CE_REMOVE_TAG). Flying wasn't among them last time I checked. The list of tokens that can be added is BLOODSUCKER, CAN_LEARN, CAN_SPEAK, CRAZED, EXTRAVISION, LIKES_FIGHTING (or LIKESFIGHTING), MISCHIEVOUS (or MISCHIEVIOUS), NO_CONNECTIONS_FOR_MOVEMENT, NO_DIZZINESS, NO_DRINK, NO_EAT, NO_FEVERS, NO_PHYS_ATT_GAIN, NO_PHYS_ATT_RUST, NO_SLEEP, NO_THOUGHT_CENTER_FOR_MOVEMENT, NOBREATHE, NOEMOTION, NOEXERT, NOFEAR, NONAUSEA, NOPAIN, NOSTUN, NOT_LIVING, NOTHOUGHT, OPPOSED_TO_LIFE, PARALYZEIMMUNE, SUPERNATURAL, TRANCES, UTTERANCES.
Web spinning can be added through CE_CAN_DO_INTERACTION, as Tomi says, which would look somewhat like this:
[CE_CAN_DO_INTERACTION:START:0]
[CDI:ADV_NAME:Spray web]
[CDI:INTERACTION:MATERIAL_EMISSION]
[CDI:USAGE_HINT:ATTACK]
[CDI:BP_REQUIRED:BY_TYPE:GRASP]
[CDI:MATERIAL:CREATURE_MAT:SPIDER_CAVE_GIANT:SILK:WEB_SPRAY]
[CDI:TARGET:C:LINE_OF_SIGHT]
[CDI:TARGET_RANGE:C:5]
[CDI:MAX_TARGET_NUMBER:C:1]
[CDI:WAIT_PERIOD:300]
I'm pretty sure that CE_SKILL_ROLL_ADJUST cannot distinguish between skills - it's an all or nothing token as far as I know. The format is [CE_SKILL_ROLL_ADJUST:PERC:150:PERC_ON:100:START:0], which would increase the skill rolls of the creature by 50%, all of the time.