I travelled by Zest air, although Sea Air also do the Manila - Tudgan (Tablas Is) route. They use small MA60 Turbo prop aircraft which climb quite high and are relatively smooth.
For domestic travel you need to pay a "Airport Fee" on departure, varying between P200 at Manila to P20 at Tudgan.
The Manila terminal is at the Domestic airport across the runway from the NAIA International airport but different and not connected. Best get there by a metered cab. Airport taxis while reliable are more expensive so choose you own path on your return. There are coffee lounges both before and after entering the departure lounge.
The Tudgan Terminal is in the village at Tudgan. There are a few small Sari Sari stores selling basic items of takeaway bars etc. There is no accommodation here, the closest being in Alcantra. There are heaps of tricycles, a few vans and a couple of Jeepney to take you wherever.
Jeepney are the brightly decorated WW2 troop carriers used throughout the Philippines. Generally around P40 for a trip between most places 1 hour.
You will be travelling with the locals and it gets squeezy. If you need to get off at the last stop I recommend getting a seat up the front to avoid the inevitable congestion. Don't be afraid to ask the "conductor", thats the guy hanging off the back, to notify you of your stop if you are not sure.
The routes are marked clearly on the outside of the Jeepney, but look for the small placard in the front window which will show the final destination. it could be going the long way around!
Note there is only one Jeepney doing the San Agustin to Looc route and it leaves at 6AM, 2 hours so P80.