I have been doing some reading and they say one of the best ways to do it yourself and maintain decent pressures for each fill is to set up a 2-3 tank cascade system...
They figure filling a 3k tank will result in a rough Scuba tank pressure drop of 200psi. So you hook up to tank #1 and the two bottles equalize at ~2800psi. You then hook up to the second tank and they equalize at ~2980. The next fill the first bottle equalizes at ~2600psi, then the second would bring you to ~2950 or so...They say this method with three tanks would get you in the neighborhood of 20-25 fills...Following is the link to where I found my info...
http://www.scubatoys.com/store/Paint.../whichtank.asp