Is it possible to use both push and pull, initially sending modules and software using pull, then push for the actual configuration ? If so, what is the best way to achieve this, partial configuration ?
Not really. You can do partial configurations with some pushed and some pulled, but to switch wholesale from one to the other you'd have to push a new meta-config to the LCM. You CAN push the configuration MOF, and have the LCM pull resource modules as needed from a pull server. "The DSC Book" kind of goes into all those permutations, if you're interested.