TS BS 180s have become my go-to TS spin. Love that trick and spinning TS BS in general. I agree, sw hs fs 3s help a lot with muscle memory and all parts of the toe back 180 except for the take off. Honestly I catch myself doing this trick two different ways, Ill explain both to give you ideas but you can choose whatever seems easier.
1-come in harder than normal and more squatted than normal, then let off your edge/flatten off a little bit in the trough so you can lessen the line tension and get straight up pop. After you let off, really push off straight up off the top of the wake. This letting off your edge also helps you get over your board more in the spin so you land more on your axis and not back foot heavy or anything. The downside of this technique is the lesser line tension and flattening off means the spin/handle pass doesnt happen until later in the air, making it harder to spot your landing. This is the technique I have seen many pros use for on axis ts bs spins. Jeff Mckee on TS BS 3s, and Collin Harrington on his TS BS 5s. They also like to come in with their arms out a little bit so they can cheat a little by pulling their arms in to initiate the spin at the top of the wake.
2-The other way I sometimes do this trick is to take a little shorter of an edge and make it progressive, not letting off my edge. I accelerate through the wake and pop straight up, but since I am on a pretty good edge when I take off, I kind of cheat the spin and use my edge to shoot me into the spin right off the wake. The plus is that the handle pass happens very early and Im done with the spin sooner (easier to spot landing, and easier for me to take to TS BS 3). The downside is that its harder to get over your board since you are shooting right into the spin. I often end up nose high off the wake, then landing with my chest down on the landing.
Id probably recommend the first way, but do whatever you want, maybe youll find the 2nd easier. Good luck, its an awesome trick.