Dick's book outlines three methods to control the contrast of platinum/palladium prints. He discusses each in the section on "Choose your method." The three methods are (using nontechnical terms) 1. The standard method. Use Ferric Ox. 1 + FO 2 in different proportions, the contrast agent is in the second bottle of FOS. By following the drop schedule for the two FOs, one can adjust the contrast of the print. The chart relates the platinum print to the paper grades on silver enlarging papers. In using this method, one uses a "straight developer", one with no contrast agent added. The problem with this method is that with flat negs, you have to use a lot of F02--which leads to all sorts of print problems like "grainy" prints.
2. The NA2 method. This is the method that Dick emphasizes in the second edition of the book. NA2 is combined with the FO1 to control contrast. The main benefit to this method is that one can print very high and low contrast images without the problems in the traditional method. It's particular benefit is that you can use a pure or very high palladium mix for the emulsion. This makes the prints very warm and very long scale. Palladiu is about 1/4 the cost of platinum. The down side is that you still have to mix the chemicals for each print. If you want to change contrast, you have to do a new batch of coating for the paper.
3. The contrast agent in the developer method. In this method, no FO2 or NA2 is used in the coating. The contrast agent, usually Sodium Dic. is added to the developer Pot. Ox. For example, to make developer solution #3, 4 drops of Sod. Dic. is added to each 200 ml. of developer. To make #4, 8 drops is added to each 200 ml. It is my understanding that this method only works with PO developer. I have not tried it with other developers. The down side to this method is that you have to keep a different bottle of solution for each contrast grade, up to eight different bottles. In practice, I only keep three bottles of developer, #3, 4 and 5. My negs generally print within that range, with most printing on #3.
Which method you choose is up to you. There are advantages and disadvantages to each method. Personally, I use the third method for most of my prints. The main advantage to me is it speeds up the test strip part of the process. When I print, I usually have a pretty good idea of which contrast level to start with. Using this method, I will often cut an exposed test print in half and develop one side at #3 and the other half at #4. I can then compare the two halfs side by side. Also, I can coat multiple peices of paper at the begining of a session and print different contrast negs just by changing developer.
If I have a very contrasty neg, which will not print on #3, I usually go with the NA2 method and straight PO developer.
Any of the methods can be used to make great looking prints. Which you choose should be based on your work flow, budget, and other variables particular to you.
One thing I do recommend is to keep the variables to a minimum when starting out. Decide if you like warm, neutral or cold prints. Pick an emulsion mix based on that choice, and then stick with it until you have printing with that mix down. Pick one developer, again based on print tone, and stick with it. Based on the above two choices, pick a method to control contrast and stick with it until you know its limitations. Once you have one method down, start playing.