I'm transitioning from active duty to national guard in March of 2019. Can I transition straight into an AGR slot?? How would I do it?

Talk to the training NCO of the unit, or Bn. that you want to transfer to.

I'm not going to tell you it doesn't happen but you have to be hired into an AGR position. There has to be an opening in the state you're joining and you have to apply and get interviewed. My recommendation is to look at the GKO portal, click on the state you are looking to join from the map, go to the HR section and look for AGR and Technician openings to see what they have. Best of luck to you.

It is possible, but it is rare.To go AGR from Active Duty, an AGR position has to be vacant and posted for nation-wide hiring, open to Active Duty ETS-ing in the time frame. You would have to submit a packet and get selected for the job.
It is also possible to get hired as an AGR recruiter.