The best formulation is a mix: indanedione with ZN in a single formulation. Hence it is a one-step process. Compared to Indanedione alone, the addition of Zn provides a much higher sensibility.
The comparison against DFO: Our laboratory has obtained better results with Indanedione-Zn compared with DFO. We have switched to DFO. Similar to the results in Australia: Stoilovic, M., Lennard, C., Wallace-Kunkel, C., and Roux, C., "Evaluation of a 1,2-Indanedione Formulation Containing Zinc Chloride for Improved Fingermark Detection on Paper", Journal of Forensic Identification, vol. 57 (1), pp. 4-18, 2007.
Note that in the UK DFO is still recommended by CAST: Sears, V., Batham, R., and Bleay, S., "The Effectiveness of 1,2-Indanedione-Zinc Formulations and Comparison with HFE-Based 1,8-Diazafluoren-9-One for Fingerprint Development", Journal of Forensic Identification, vol. 59 (6), pp. 654-678, 2009.
To understand the role of Zn on the process, see the excellent:
Spindler, X., Shimmon, R., Roux, C., and Lennard, C., "The Effect of Zinc Chloride, Humidity and the Substrate on the Reaction of 1,2-Indanedione-Zinc with Amino Acids in Latent Fingermark Secretions", Forensic Science International, vol. 212 (1-3), pp. 150-157, 2011.
University of Lausanne