I have tried just about every method mentioned in this thread except the "jiggle frame" and discard them in favour of the method I'll describe, mainly because I find it quick to set up and very effective.
For burning in I use a piece of black card that has become very pliable after years of bending into the shape required to burn in the area in question. When the card was new and was bent to a shape it cracked so I taped it over with masking tape. After a few years of doing this it became very soft as I was able to bend it form just about any shape I wanted. I got the idea from this to use a piece of heavy industrial rubber, such as the sort used on entrances in warehouses where forklifts etc run through. This did not work so I returned to my bit of black card. Apugers who attended my workshops in San Francisco and Calgary will tell you how effective it is. When burning in hold the card as near to the lens as possible, this producesa penumbra which is a wide softened area that is projected on to the baseboard which allows you to feather the area being burned in to the adjacent area that you are holding back.
For difficult dodging I lay 3 or 4 boxes of paper on the base board and place a piece of white light card and project the image on to it. I then draw around the area to be dodged, cut out the shape making the edges ragged and stick it to a piece of flower arranging wire. I remove the boxes project the image and by holding the dodging tool at the same height as the boxes were, thus ensuring that the size of the dodging tool matches the size of the area on the baseboard to the area being dodged. A slight up and down movement ensures that there is no tell tale halo.