As mentioned, delidding is usually done for cpu's that were extremely poor in terms of thermals to try and counter a factory flaw. Mx-4 won't be any better than the tim under the ihs if it's as good. The other reason is extreme overclocking. Lapping may help if the ihs is seriously flawed or if using a cruddy cooler that has a poorly machined base. Not usually the case anymore.
I've lapped heatsinks in the past but that was years ago. It wasn't unusual for many coolers to have cheaply milled bases that weren't flat. Today's coolers are often much better and can be checked with a straight edge like a metal ruler. Another thing to consider, a cpu's ihs should only need lapped if the edges are higher than the center leaving a low spot where there'd be an excess of thermal paste required. Usually a cpu's ihs is slightly convex to help ensure solid pressure/contact with the cooler base. If you lap the cpu itself not only is the ihs fairly thin to begin with you might make it worse than it was to begin with.
You're welcome to play around with things as much as you want but it helps to understand why you're doing something. There were reasons for making various alterations, many of which just aren't needed or won't have as much impact these days. Overclocking to 3.6 is barely overclocking. The cpu is already designed to run at 3.6 on turbo boost so basically a 3.6 'overclock' would be forcing all 4 cores to run at their designated turbo speed.
As an example I have an i5 4690k running at 4.6ghz, 700mhz over its turbo boost speed on all 4 cores. Granted I'm using a decent large air cooler but my temps are fine, the cpu uses tim under the ihs, the cpu wasn't lapped or delidded, the cooler didn't need lapped (it was machined well to a mirror finish and true out of the box). It's really not necessary.
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