The fees are only one form of generating dust, and therefore holding BNB will not help your dust problem. Conversion from one currency to another as a result of trade will generate fractional amounts in the end currency almost certainly. For many currencies, Binance will simply round off the amount you want to trade to a whole number, whether you have BNB or not, leaving the fractional amount in the source wallet. The only way to bring the holdings in the wallet to zero would be to 1. hold BNB (so the fees don't bite into the transaction, generating fractions again) and 2. Depositing exactly enough of the currency into the wallet so as to have a whole number of coin, which can then be removed. You could do it without holding BNB, but then you'd have to deposit some rational number such that once the fees are taken out, you get a whole number again.