How can I switch from the AF to CG?

The coast guard is very Coast Guard eccentric. You will go through a full boot camp and unless it was a joint school a full technical training cycle. Here is a little good news if your current MOS translates directly to a coast guard rate as an E-3 you will only loose 1 rank. if you choose a rate that you do not have any training in such as boatswains mate you will most likely be starting all over. And lastly you will be known as the air force guy.

The "shortened version" of Basic was what the Army required for prior service AF and Navy. That no longer exists.
Another branch either accepts your basic training and allows you to skip theirs, or you go through their whole basic.
There is no shortened version for tech school, AIT, AFSC or A School.
If your current specialty wasn't taught at a tri-service school that all branches accept, or if your current specialty does not directly translate to a specialty or rate in the component you are transferring to, then you will attend a complete tech school for that branch.
The rest of the details are that you get a DD 368 Conditional Release approved by your component to leave early to join another component, or if they say no, then you line up a recruiter six months out from your ETS to join that new component on the day after your ETS.

Please you are changing complete life styles, what in the USAF can relate to small boat, ship handling- rescue training, etc. If that USCG is what you really want then be prepared to do it their view, and stop looking the easy way!