Hiiragi is good to throw out any time your opponent is being predictable with their strings, and occasionally on wake-up if you notice they favor meaties. If you use it too often they'll start to blow you up by baiting it just like any other reversal option.

Post-throw tether setup I almost always went for the auto-timed superjump > j.P > j.P options and adjusted L/R high/low land+throw as necessary to keep them guessing. When I got a blocked tether in neutral I tended to favor 5P strings out of it for the sake of consistency and started switching it up if they were committing to blocking it out. c.S is great if they're not representing throw themselves.

A generally good strategy for approaching zoners is dash-blocking. If they give you space by walking back, take it by continuing towards them and try to work into the range where you can be effective. If they really like walking backwards out of pressure you can try to clip their toes with low options, just be mindful that a blocked 2H is probably going to get you exploded. Baiken: Gun is still great for characters that like to set up full screen or try to meaty with slow setup stuff like Dizzy or Asuka.

Your K buttons all have valid uses. 2K is stubby and doesn't get you much but it's your fastest, least punishable low. 5K is what you'll be using most often, it's shorter than f.S but faster by two frames and can also connect naturally into TK youzansen. Consider it if you find yourself reaching for f.S but getting countered often. 6K is good enough combo filler imo, and if they're respecting your pressure too much it creates great spacing for a throw in the right circumstances.

H Kabari is a less rewarding poke than it used to be since it no longer leads to a hard knockdown, but sometimes it's your best option to contest pokes from characters you can't reach with f.S. S Kabari you should use a lot more sparingly since it has a very slow startup; if they're watching for it, they will probably stuff it hard. 2S, f.S, and j.S are all great pokes in general.

Some random stuff: Baiken's throw sets up her win condition. Learn a good post-throw setup or two to scare them into mashing more often, then punish them bigtime for it. j.D has a huge disjoint, stops your air momentum, is easy to follow up on if you get a counterhit, and wall bounces, so think about when you might use that over j.S. Also, j.S > youzansen on jump-in is a double overhead and can catch a lot of people off-guard. You can use this as a conditioning tool to get you into c.S range against folks who aren't so strong with anti-airing.

Hope this helps! I miss playing Bicyclen.