I've solved this using self.pool.get('obj_name').create(cr, uid,values) to create new entries in that second table.

used this function:

def insert_trace(self, cr, uid, id_request, context=None):
    request = self.browse(cr, uid, id_request, context)
    values = { 
        'generic_request_id':  id_request[0],
        'executor': self._get_user(cr, uid, context),
        'state': request[0].state,
    }
    tracing_ids = self.pool.get('tracing').create(cr, uid,values)
    return True

and called it, each time workflow changed, e.g:

def request_draft(self, cr, uid, ids, context=None):
    self.write(cr, uid, ids, {'state': 'draft'})
    self.insert_trace(cr, uid, ids,  context)
    return True

def submit_request(self, cr, uid, ids, context=None):
    self.write(cr, uid, ids, {'state': 'submitted'})
    self.insert_trace(cr, uid, ids, context)
    return True

I'll leave this here, to help anyone with the same problem that I was having.