Look at Glen Feron - retouching for advertising.
Remove crease and patch lines from scans, smudges from hand on paper etc.
These techniques work for anything with lots of detail.
If it's an original, make sure that you save an original copy.
Zoom in very very close - under bandaid - healing brush and patch.
Healing brush - get a big brush head, go and make it an appropriate size to what you're retouching. We also want an oval rather than a circle - drag anchor points in to make an oval - the circle can be too obvious on skin etc.
Zoom in further, but it matches the colour to the surrounding colour. Blends in with background colours.
If you want a bigger area, use the patch tool. Select an area that you want to replace, hove mouse over area, drag it to an area of the same pixels that you want.
There is a dust and scratch filter - filter --> noise --> dust and scratch - this blends any abnormal marks to the background.
In adjustments, cnage contrast between highlights and shadows. Bring up tone of paper by playing with levels. Make sure that the levels are a different layer, very hard to get back to what you started with.
Getting rid of red eye - at the bottom of healing tools - just click on the centre of the pupil, and it will change this.
Photoshop brushes - work in a similar way to illustrator, but they are pixel based not vector. Can't scale to be bigger.
Brusheezy - good site.
Opening a new brush library - ask to append, it adds the brushes on rather than eliminating the brushes.
Edit any existing brushes by opening brush presets and fiddling - size, orientation etc