I really don't know the grades because I don't know all the boulders or lines. I think the rock is mostly granite. Some of this is high-balling.
There are at least 2 good boulders on the main trail (names unknown, but one was said to be 5.9 = VB or V0). But I found boulders all over the place, so have fun exploring.
As you find projects, add your beta to this post. The more, the better. Thanks.
Lonely Planet Korea says "Take subway line 1 north to Dobongsan Station.... Exit the station and follow the other hikers across the road, through the market and food stalls and past a bus terminal to the ticket booth." Just following the other hikers worked for me since it's such a popular place.
Bring a couple crash pads and a couple friends for the taller projects.
Since it's a national park, access to the needs of the masses is plentiful down low, but don't look for restaurants at the top like you'll find in other parks.