ok i remember....
first open up the photo you want to dodge or burn
click on the "add new layer"
unclick the check box for "background" ....make sure the "layer" is highlighted in blue.
open up the colour window by clicking "window" then "colour" then "more" place your cursor next to the "0" in "hex"
now delete the "0's . now type in 888888, that will give you grey
now click on the "paint bucket" in the tools section..... click and fill the layer with grey....
now type F4 ..... then the drop arrow for "blending mode" then click on "overlay" then "ok"
now recheck the box for "background" you original image will appear....
go to the colour window and depending on what you wish to do.. change the "V" lower numbers for darker and higher for lighter.
also, change the "transparency-alpha to about 8 for subtle dodging or burning, less harsh edges....
now click on the "paint brush" in "tools" and then select the size "width" ..
so.... after using the brush ....... click on merge
i found the above technique somewhere and it works for me..