I take the valves out of course. Marking which ones goes where. The springs hardware and all. Clean the best I can with brake cleaner. Then I glass bead blast. Everything. The whole head. Clean well. I just use hot soapy water with a brush. Clean again. Clean again... Haha. Check spring tolerance. New seals. Lap valves. Leak test.
Edit: if your head looks this bad, better take the valve cover apart. Remove rockers and clean oil passage ways. Like everything, there's a mod on here for the rocker arms. I went ahead and bought aluminum rocker caps to replace the old. Hard to remove the old caps without visible damage.