You can test the result of your fixing with a silver nitrate solution. Details are in Kodak publications. If the test shows fixing is complete, it does not matter whether you use one or two baths. Two baths are used mostly for production environments to obtain maximum life from the fixers before discarding. The second bath is discarded and the first one becomes the second bath with new fixer for the first one. Fixing is either complete or not so if your present method works there is no need to change it. If you are not re-using fixer you are unlikely to exhaust the one bath.