The simplest implementation for this, if it doesn't conflict with other scripting, is to create a character script that has a reaction, which executes a simple CharacterAttack and a Sleep between each of the attacks.
Something along the lines of
INIT
EXTERN ITEM:%Target=null
[...]
REACTION Training, 100
USAGE PEACE
ACTIONS
CharacterAttack(%Target, 1)
Sleep(1)
Then, you can create a few indestructible objects (dummies, targets, etc.) and set them as targets for your training NPCs.