I'm hearing two basses.

The 808 drum hit sounds a bit saturated / distorted / overdriven and EQ'd, just try playing around with a high quality 808 sample that has the same decay setting.

The second bass sounds a little higher up in note, which can be easily made on any synth - Sine Wave. Then again just saturate it or use tube distortion to achieve the same sound.

Once these are made, just side chain to the kick drums to taste. 

Don't worry about getting it exactly right, just keep messing around with saturation, tube distortion, overdrive. Careful not to overdo it, as your sub will get lost in the distortion.

Ok, so I've been layering kicks and am pretty happy with the results. But one thing I've found quite difficult is getting that clicky high end.

A good example is this track by Com Truise: https://www.youtube.com/watch?v=F2mkAywo61o

I've discovered that putting some cabinet simulation on the top end really warms it up, alongside picking the right sample in the first place.

Can anyone shed any light on what else might be used in the example? I'm hearing some heavy compression and really good transients on the drums.

This could be one way: https://www.youtube.com/watch?v=HLUXldeGg64

Also, please post any other tips you have for layering drums.