I've had always managed to get empowerment whenever I felt like it. However, I read active god X's religion first and try to build the char concept around that in some way (matching desired race/align/cabal to the god). But twice I had an imaginary god and that worked out alright too, albeit took a little while longer. Usually the whole process takes about two-three weeks of slow leveling, praying in shrines (or appropriate places) and inn hangouts. If you're on, say, every other day for two-three hours at a time when your imm is likely to be around, it's easy-peasy.
However, if your chosen god is (semi)dormant or the char concept just doesn't fit into the religion (or your understanding of it) then I can see if this could be difficult.