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Even if superficial trace evidence is absent, a second autopsy can be expected to verify the number, placement, and track of the bullet wounds and may also yield samples for toxicology testing. Moreover, the pathologist conducting a second autopsy may obtain notes and test results from the first autopsy and integrate them into his analysis.

In this instance, the second autopsy doctor, Michael Baden, is a justly well-regarded pathologist and seems unlikely to risk his reputation by cooking up autopsy conclusions to satisfy the media or the Brown family.

Gunshot residue particles can be removed easily from the surfaces they land on. Regular activities, such as putting hands in pockets, rubbing hands together, or handling items, can wipe them away.4 The washing of hands can remove most, if not all, particles. Rates of loss vary widely with the activity of the subject. Depending on conditions and activity, particles may be removed from a shooter’s hands within 4 to 5 hours after a shooting event.5 They also can transfer from a surface or person to another individual; the amount depends on the number of GSR particles on the contaminated surface (e.g., a person’s clothing or hands) and likely will be a small percentage of the total number of particles present.

http://www.fbi.gov/stats-services/publications/law-enforcement-bulletin/may_2011/The%20Current%20Status%20of%20GSR%20Examinations

Are you talking about residue around Mike Brown’s wounds? Or about residue on Mike Brown’s hands?

If you’re talking about the wounds...

First, the lack of gunpowder residue works in favor of the policeman, because it shows that Mike Brown was not shot at close range, execution style.

Second, the body shots would leave residue on the clothes. And the clothes had better not have been washed.

If you’re talking about Mr Brown’s hands...

The lack of residue would indicate that Mr Brown’s hands were not on the gun when it fired. But as far as I know, no one is saying his hand was on the gun. It has been suggested that the gun fired while the two men were struggling, but that is not the same thing as saying that Mr Brown pulled the trigger. And we haven’t yet heard the policeman’s version of the events. At least not officially and in full.

My question is would the washing of the body done in the first autopsy as well as other procedures remove the far trace. If so the claim the was no far by the Brown family team would be misleading at best.

I think that the second and subsequent autopsies have to rely on the first for certain results, and are limited in some ways because there was a first to start with.

See:

What a Second Autopsy Can -- and Can't -- Reveal
Because timeliness is critical, if you suspect foul play in the first autopsy, do not trust the first medical examiner or would like a second opinion for quality assurance, you must make the choice of whether or not to have a second autopsy performed fairly quickly after the first autopsy, and usually without its full results.
Alabama forensic pathologist Dr. Jim Lauridson, who is often called on to perform second autopsies, says that a second autopsy very often finds information not discovered in the first autopsy. Even so, he says there are certain limitations because organs have often already been removed and dissected, and the fluids necessary for an evaluation are now no longer available.
Additionally, certain tissues can be retained by the pathologist at the time of the first autopsy and may not be available for examination. But a second autopsy often looks at parts of the body that were not examined in the first, and the incorporation of its results, with those of the first autopsy and other available medical and investigative records, can depict a far more thorough and comprehensive picture of the cause and manner of death.

Autopsy 101, Frontline