If Lightroom looks like a piece of cake, then you might want to try a more powerful program called Adobe Photoshop. Now I myself am not an expert at photoshop, however I can show you a few features I have learned.
Content Aware Fill
This amazing feature allows you to, in essences, delete objects (i.e. People, Trees, Buildings, etc.) from your picture and maintain the look of the picture. It does this by filling in the area you define with pixels that the program determines from looking at the surrounding pixels. Below are some examples of the feature. I quickly went through and applied the effect so the quality is not perfect.
Color Inverting and coloring
The next effect is actually two effects the first part is color inverting. This basically takes the dark colors and inverts them to light colors. Then the second part is a gradient color overlay. Using this effect is how the smoke photo’s were created. However, the gradient color overlay can be used on regular pictures to make a neat effect on the picture as shown in the second example.
to see how to take pictures of smoke like these check out how to for smoke photography.