If you are determined to use the oil based liquid, the only suggestion I have is to use an atomizer and direct drip. You might also want to try using the LR versions or a high voltage device. The LR will burn hotter than a standard atomizer and a higher voltage device will make the standard atomizer burn hotter. I don't think it is the coil getting clogged, I think it is the filler in the cartomizer becoming saturated in oil and doing the clogging.
Also, using either of the suggestions above, could alter the flavor of your liquid and you might have to add more of the oil. This could prove to put you back at square one.
