viajero- hard to provide advice without knowing what your situation is. Are you currently living in Canada or the US? If in the US are you on some sort of work or student visa? USCIS states that form I-29 is:
For petitioners filing on behalf of an alien to come to the United States temporarily to perform services or labor, or to receive training, as an H-1B, H-1C, H-2A, H-2B, H-3, L-1, O-1, O-2, P-1, P-1S, P-2, P-2S, P-3, P-3S, Q-1 or R-1 nonimmigrant worker. Petitioners may also use this form to request an extension of stay in or change of status to E-1, E-2, E-3, H-1B1 or TN, or one of the above classifications for an alien.
If you are a Canadian for example, with an employment offer from US company, you could apply for TN yourself at any port of entry. Assuming you have all required paperwork complete and are accepted, you would get TN same day.