The short answer: take everything the Western powers tell you, do the opposite, and ignore them when they complain. From Indian Defence Review:
"Fundamentals of Victory against terror - Sri Lankan Example."
A few thoughts here.
One is that this model applies best to domestic or contiguous terror or guerilla fights, because those sorts of fights are the most existential, and control of territory for however long it takes is an inherent requirement. That doesn't mean it's impossible to apply to foreign fights, but the question must then be asked: "what for?" There's an answer in a colonialist framework, and there are answers within punitive expedition frameworks (like, "we're going to flatten towns involved in Somali piracy"). I'm not sure the Rajapaksa Model would translate in a place like Afghanistan, though elements of it could still be useful.
Another observation I'll make is the unspoken factor of Sri Lanka's cultivation of China as an alternate source of arms, removing dependency on (and hence pressure from) western suppliers.
That "no dependency" imperative is one I'm already seeing come to the fore in places like Indonesia and Brazil. Sri Lanka's experiences just add more fuel to an emerging consensus that the Western/UN approach just breeds disorder and failure. Now throw in the proliferation of new/revamped defense exporters around the globe in countries like China, Russia, South Korea, Turkey, Brazil, South Africa, et. al. Put that together, and I expect to see more countries take the Sri Lankan approach. The days of Western arms embargoes meaning much, or accomplishing much beyond costing Western jobs, are coming to a close.
Speaking of India, their naval intelligence cooperation, which allowed Sri Lanka to shatter the Tamils' supply network, adds an interesting wrinkle. At the distances involved, it looks like India used its fleet of TU-95 "Bear" long-range maritime patrol aircraft. Those could be considered a strategic national asset, so it was obviously a high priority task. The Tamil Tigers assassinated Rajiv Ghandi back when, so it's not surprising that there might be a bit of a grudge. As paybacks go, this turned out to be a pretty good one.
By the mid-2010s, when India has its new 737-derived P-8i patrol aircraft and a fleet of 3 carriers, it will be positioned to do this sort of thing in an arc extending from the Straits of Malacca to Suez and South Africa.