Soot forms naturally during combustion of the gasses and can only be reduced by burning less gas in your fireplace. A vent free set will burn less than a vented set and as a result will soot less. But the short answer is that no, sooting cannot be avoided and the logs or whatever set is in your fireplace will collect more soot the more they are burned.
However, soot can be removed from the set in an easy way. Turn on the fireplace for a few minutes to get the logs, balls, or whatever nice and warm. After that, spray the sooted areas with a spray bottle, then turn off the flame. The soot will be dislodged and will go out the chimney as the set burns. They can also be taken out while cold and washed and brushed, but this is not recommended.