I've only ever had one failure with this method, and it did ferment eventually, it was just too late. Leave about 30ml in the bottle when you pour it, and add about 30ml 1.04 dme solution. Cover with sanitised foil and give it about 3 days. Then add that to 300ml at 1.04 on the stirplate. After that you should be able to do the final step to pretty much whatever you want to reach your desired cell count. I only ever cool and decant if my flask can't handle the volume.