History brush stopped working when I was almost done

[Challenger Gibraltar]

Can anyone please help.

I loaded my raw image into PS desktop (Mac) I created a duplicate layer and turned it b&w, I then selected the history brush and started to paint of the butterfly bringing back the colour. I had spent an hour on it and was almost at the end when the history brush stopped working. I contacted help line via chat, they suggested using the quick selection tool and also select auto-enhance button at the top. I don't have a auto-enhance button, I have Enhance edge button. Anyway I tried their suggested method but the butterfly is too intricate for the use of the quick selection tool, so I am left with a butterfly that is not yet completed on a b&w background, can someone please help me. I am disbaled with a head injury so I need easy instructions please. Thank you for you help.

Paul 

[Bojan Živković]

From what I can understand you want to reveal buterfly which is on layer beneath BW version of the same photograph. To create selection using brush you have several options:

• Paint with brush on layer with lowered opacity above BW image. When you finish use Ctrl + click on layer's thumbnail to load content from layer on which you have painted as selection. Use selection to mask content on BW layer and to reveal colored buterfly.
• Another method is to create layer mask for BW layer then to paint on it using black color to reveal colored buterfly beneath.
• Press Q on your keyboard to enter Quick Mask mode then paint with brush. Once you are done press Q again and Photoshop will load selection which you can use to delete or mask content on BW layer.

[Katie Houghton]

You need to take a snapshot of the state you want to brush back to with the History brush. 

1. Your orignal History panel will look like this.
   Original File
2. After you copy the layer take a snapshot of the current state. The Camera icon in the History panel creates a new state. It will say Snapshot 1, 2, etc. I changed the names for explanation.
   
3. After you turn that layer B&W then take a snapshot of that current state.
   
4. Finally move the brush icon in the History panel to the state you want to paint back into with the History brush.
   
5. I make the B&W state so I can draw back to the B&W state if I make a mistake.
   
6. If you did not want to use the History panel and History tool  you can also add a Layer Mask to the B&W layer then brush back into the layer mask (The layer mask is selected and you can tell since it has a bounding box around the layer mask and not the layer icon). When using the regualar Brush tool,  you brush black into the Layer Mask to hide the B&W layer or brush in white to show the B&W layer. When you hide the B&W layer you will see the color layer that is placed just below the B&W layer.
    
   
   
   I hope that helps and answers your question.