If you are looking for a more subtle change, I'd start at 1:25 or higher. If it goes too far, there is no saving it. If it isn't as far as you'd like it, you can always tone further. With high dilutions, I find that having an untoned print in tray filled with water next to the toning tray helps to monitor the tonal change. If toning takes, say, five minutes, it is hard to really see the changes without a reference print next to it. And, yes, HCA is a good idea after selenium (at least according to Kodak) to reduce wash times, but not necessary if you are doing an extended wash anyway