If you have a pump, or an extra keg you don't need to remove the dip tube (it can really jack up the keg if you do it wrong). Use the same technique described above for transferring the beer, but with a keg full of your caustic, rinse water, or sanitizer. Be very thorough with it because you won't be able to visually check the keg for sediments or debris. Let the cleaner sit and soak for a while with frequent agitation (shake it) to ensure you get everything, pump it out with a regular gas in, beer out hook up till it's empty. You can rinse the keg by doing the same thing a few times with water, or by running water IN to the beer port on the sankey, running another hose out from the gas in port to a drain(replace the check valve with a standard O ring), flip the keg upside down (can brace it with a couple of chairs) and pump the water in to throughly rinse the cleaner out. Finally repeat one of those techniques with the sanitizer. Thats essentially how many micro breweries do it, except they've got big tanks and pumps for the caustic, rinse, and sanitizer and fancy stands to brace the kegs on.