Thanks, all. Robert, the toning was carried out sequentially with a short bath (1 minute) in selenium 1:9, wash in plain water, a short soak in the thiocarbamide toner (10 seconds) with the coldest dilution (5:1 NaOH:thiourea), a soak in the bleach, rinse in water, and then reimmersion in the thiocarbamide toner. The times in the bleach bath vary from image to image depending on how far down the tonal range I want to introduce tone.
Hope this helps.