Fill quantities vary, from one manual to the next. Generally speaking, they overlap around 3.8oz+/-, for a dry fill. What no manual will tell you is the optimal quantity for YOUR fork. The only way to determine that is with a little extra attention when doing the initial fill...followed with some road miles to check the result. Fill quantity can make a much bigger difference than seems possible. It's a little tricky, if you've never done this but, in reality, it's rather straightforward. As you reach the limit, suspension action tightens rapidly. 5cc can make the difference between optimal and too stiff...or even hydrolock (before the fork can bottom-out). This varies due to production tolerances, internal wear and oil viscosity. Start with 3.5oz. Then, with the fork leg fully compressed, look inside. Add 5cc of oil, at a time, until you can see the oil level ~6" below the cap threads. At that point, finish assembling the fork, on the bike, then test the front end action. If you can bottom-out the fork easily, front wheel braced against a wall, workbench, (or using the front brake, if it'll hold), try adding 5cc more oil, then retesting. If you can't quite bottom-out the front end, or you really have to jump on it...time for the road test. If you're happy with the suspension action, you're done. OTOH, if it's still too soft, go back to the "add 5cc and retest" mode, until you either get what you're after or you reach the point of reduced fork excursion (hydrolock), then remove the amount of oil that pushed things over-the-top.
You can use the drain bolts on the fork legs, just be careful with the torque. They don't need much. If you source a large syringe...and they are made for this type of use...it makes life a lot easier.