Hi Pow. I'm using an RN4081 right now. My 510 should be here soon. To fill the cartridge on yours, use a straightened paperclip or a straight pin and insert it into the little hole where you put your mouth. You can then push the cartridge up to the end that plugs into the atomizer and fill it. It will only take 3-4 drops. You've gotten juice, I take it?
The RN4081 is an excellent little atomizer.
It is very good for dripping.
The problem is that dripping can be an issue when using automatic batteries.
If you aren't really careful, you'll get some juice in the battery.
And that can gunk it up and make it stop working.
I used to drip with mine and was careful about not flooding it.
And I never had a problem.
But if you get a manual battery for that RN4081 it is really great for dripping.
If they had manual batteries for RN4081s when I started, I might still be using them.
If you Google "RN4081 manual battery" you will find a couple of places.I have a 4081 Smoking Everywhere which really isn't bad. Where can you order the manual batteries? That would make it better for sure.