What is the best way to make custom color profiles for the Epson 3800?
That all depends… If you are new to creating custom profiles, I suggest taking a look at Bill Atkinson’s color downloads page. Bill has made his excellent profiling targets available for free. Download the Targets FAQ and read through it carefully — it has lots of good advice. I personally use the RGB 4096 Eye-One target (printed on three 11″ x 17″ sheets) for PK papers and the RGB 1728 Eye-One target (printed on one 13″ x 19″ sheet) for MK papers.