The only tolerance for "gradualism" that I have is that repealing laws will take time, opting out of coercive institutions will take time, and for some people getting out of the habit of coercion will take time.
Re-establishing voluntary institutions for those things expropriated by government will also take time, but I do not think it will take very long. Adjudication, education, protection are already provided privately. Just as railroad companies cooperated to establish standards and interoperability in order to foster their own businesses, so will airlines cooperate and maintain "air traffic control", although I doubt it will look much like what we have now once government inertia has been removed.
The various satellite communications companies will continue to cooperate so that everyone gets to share earth orbit without knocking each other out of the sky, and I'm pretty sure that the various tax-funded astronomy efforts will find plenty of space-buffs to keep the money coming in.
Lysander Spooner, UPS and FedEx have already demonstrated ably that the post office is obsolete. Walter Block has done great work for roads.
So what's left to be 'gradual' about? Just get on with it already.