You can direct drip on an ego-c but most people seem to prefer other types of atomiser. I've tried with an ego-t atomiser simply by removing the tank part (the platic bit at the top) and dripping 2-3 drops onto the spike. Whilst it worked it was nowhere near as satisfying as other atmomisers I have tried. The other problem is you need to 'tail-pipe' it, (suck on the atomiser tube without a drip tip) unless you can find a drip tip to fit as they are not a standard size.
There are lots of options out there, with some atomisers being specifically designed for dripping. I have tried DSE-901's (901 thread so you also need an adapter to fit it to 510's) and like those. My favourite so far though has been a debridged 306 LR. This is a low resistance atomiser with the bridge wick removed. It gives me super flavour and a good hit. I've been using the same one for about 3 weeks and just giving it a vodka bath to clean it as I felt it was starting to lose performance. Popped it back in and its working like new again.
You can still use the ego style batteries for dripping and many are happy with this. I prefer using a variable voltage device so that I have some control over how the atomiser behave and can tailor it to my mood or the flavour I am using.
Out of the three methods of
vaping I have tried, direct dripping, cartomisers and ego style
tanks, dripping wins the flavour race for me, with cartomisers second and ego
tanks last.