Different lineages will say different things. However it is definite that in one lineage (probably at least three) you can practice Chenrezig without having had the empowerment as long as you do not visualize yourself as Chenrezig and you visualize Chenrezig in front of you, blessing yourself and all beings with compassion.
You can do this very simply, after taking reciting the refuge prayer. This doesn't have to be elaborate. Later, get the empowerment and the instructions for the sadhana you wish to do.
In general Chenrezig, Green Tara, Medicine Buddha and Amitabha are regarded as being sort of open practices like this (although not all the sadhanas and practices associated with them are). But the point is that you can meditate on Chenrezig as the compassion of all the Buddhas and visualize the blessings of Chenrezig to come to yourself and all beings.