Genome annotation is not an easy task to perform even with commercial software and reference genomes. And in your case, you dont have either of them. It is practically impossible for you to do annotation as you said "in single shot". However, you can try advice from Pritam, it's sufficient information what he provided.
You can try out our new eukaryotic gene annotator pipeline FINDER (https://github.com/sagnikbanerjee15/Finder). You can access the paper here (Article FINDER: an automated software package to annotate eukaryotic...