Hirado Castle bus/ferry access

How can I access Hirado Castle from the nearest train station, Tabiraharidoguchi or Nishitabira? Ultimately I'm coming all the way from Hakata station.

The page on Hirado Castle says there are buses, apparently, but getting some details on that is very challenging. I've wound up on this site:
http://www.bus.saihigroup.co.jp/

From there, I'm not sure which bus stops to enter when at the 停留所時刻表 (timetables) page.
I've tried 荻田 -> 猶興館高校入口 which shows the most promising (or the least unpromising :)) result so far. There is apparently a bus that runs about once per hour towards the south end of the castle park. Brilliant, but it also means a very bad connection with the train, resulting in an hour waiting time. So perhaps there is a more efficient option that I haven't found yet?

Another thing I've noticed is the precence of a ferry. Information on the ferry seems to be here:
https://www.city.hirado.nagasaki.jp/kurashi/life/sumai/koutu/ferry/fe0...

Not sure though, because the ferry looks to run only once per day, just before 8AM. So that's not very helpful either, unless I'm overlooking another schedule.

So in short, what is the best way to get to Hirado Castle?
And also what is the best way to get back to Hakata? All in one day, hopefully :)

Another option is to rent a bicycle, or even a car. I'm just trying to avoid 'wasting' a lot of time, since I've already burned a few hours getting to Tabira area from Hakata.

how about this route:
1. from hakata station, take JR tokkyu Midori to Sasebo station (90 min.).
2. u can find Saihi bus center 西肥バスセンター in front of the station, take a bus to Hirado Sanbashi 平戸桟橋 bus station. (90 min.)
3. from there, to Hirado castle is 20 minutes walk or u can take taxi. (in front of the bus stop, there is tourist information center and they have rental cycle service.)

A 20 minute walk seems totally doable. And it's a direct connection with a comfy limited express to Sasebo as well :P

Now, what would be the best place to find timtables for that bus? I feel like it's best to plan ahead to avoid long waits.

here is the timetable (japanese)
http://mori-shuzou.jp/PDF/saihibusTime.pdf

佐世保駅前 = sasebo station bus center
平戸桟橋 = hirado bridge (the last stop)

they have bus almost every hour or more.

u can also refer to the bus company site;
http://www.bus.saihigroup.co.jp/english