Great question! Well- keeping prints flat can sometimes be a job in itself as part of the old wet process is concerned. So…What I need to know from you before I write a small book on the subject; is if you are actually making analog prints on fiber base of RC silver based traditional photographic papers. Since I had spent a good part of my life in the wet darkroom, I have all kinds of lotions, potions and tricks for print drying. Believe it or not there are dozens of factors involved such as relative humidity in the room, water quality, wet-time, types of fixers, hardeners, heat and air drying, image tone stability and more. It’s all very interesting but it in no way does any of this apply to ink jet printing materials of any kind.
If you are into the analog darkroom, I am sure you will find this all very interesting. Also- if you can tell me any difficulties you have had with this issue, it will help.
Hope to hear from you soon!