Here's my procedure for local bleaching:
Prepare a dilute ferricyanide/bromide solution of about 0.5-1%. The basic solution is 0.5-1g pot. ferricyanide and 0.5-1g pot. bromide / 100ml. I have stock solutions of 10% pot. ferricyanide and 3.3% pot. bromide on hand and usually just mix from those (10ml 10% ferricyanide solution and 30ml 3.3% potassium bromide solution and water to make 100ml makes a 1% solution.) Adjust the strength of the bleach as needed. Different papers bleach need stronger or weaker solutions. I like to work with a rather weak solution for bleaching highlights and build up the amount of bleaching I need.
The print needs to be fairly free of fixer before using this technique. Four-five min. or so in running water seems to do the trick for me; some like longer.
Lay the print on an angled work surface, (e.g. the bottom of a flat-bottomed tray). Position the print so that the run-off does not flow over areas of low density that should not be bleached. Working with the running water hose in your left hand, apply the bleach locally with a brush or cotton swab (Chinese calligraphy brushes work well; brushes with metal ferrules should not be used as the metal will react with the bleach).
It is very important to keep the water running on the print directly below the area being worked on to prevent streaking by the run-off and to keep the water hose moving to keep the bleach from being directed down the edge of the water stream and causing streaks there.
Before the desired tone has been reached, rinse well. It is better to build up to the desired tone slowly to prevent over-bleaching, keeping in mind that the bleaching continues for a while after rinsing. Be careful that the bleach is not working too quickly. If so, rinse the print thoroughly and repeat with a weaker bleach solution. Overbleaching can cause split toning later if you selenium tone!
When the desired tone has almost been reached, rinse the print thoroughly to remove all the bleaching agents before fixing. Again, four or five minutes in running water works for me.
If the bleaching process goes too far, the print can be returned to the developer, but this can result in a different size and shape of silver grain being formed from the original development, which will tone differently. If redevelopment is necessary, keep toning to a minimum.
After bleaching, the print needs to be fixed to remove the silver bromide produced by the bleach.
Wash and dry as usual.
It's always better to bleach a print before toning, but you may have success on a lightly selenium-toned print. I include bleaching as part of my print manipulations and always before toning. I ruin a print or two every now and then with bleaching, either from over-doing it or because the bleached areas tone differently later. There's always a bit of hit-and-miss involved when bleaching, so I wouldn't recommend it for a print you can't make again.
Hope this helps,
Doremus