What does the zhe 着 after a verb do? mdbg.net has for zhe 着： aspect particle indicating action in progress 

That implies it corresponds with -ing. Many times however, I find 着 cannot be translated in this way.

What does 着 do? What difference does it make if it were not used?

From 父亲去世了

他光着脚，手指弯曲着，失去了往日的力量。
His leg bared, fingers bent, gone his former strength.
他的眼睛紧闭着，像两个黑洞。
His eyes tightly closed, like 2 black holes.
嘴巴张着，牙齿都露了。
Mouth open, teeth revealed.
着 is used to express that something is in the status of a verb, so it should not be progressive. For example "sitting" is 坐着.

Examples:

他光着脚，手指弯曲着，失去了往日的力量。
His leg bared(baring), fingers bent(bending), gone his former strength.

Counter-examples:
您做着什么？ This one is invalid

The verb "do" is progressive(this action is changing), so 着 is not used here.