Welcome. You are definitely doing the right thing reading and studying before acting. I believe you will find that most posters here do not use furnaces for the purpose of "separating" metals. Without telling you that I am any kind of expert or tribal elder, furnaces do not separate. Indeed, many of the more veteran posters here kind of shun furnaces for various reasons. I will leave it to you to discover on your own why they feel that is so. But one of the major reasons is the whole issue of crucibles and their cost and their limited life or, the frequency of replacement to put it in different terms. To separate metals, chemical processing is required.
One of the things I note about all that I have learned on this forum is the incredible degree to which "one thing leads to another" in PM refining. When you/we speak of "refining", this lengthy thought exercise is created....do you have access to enough material to make this worth it? Can you source the chemicals? The glassware? The safety gear? The way to handle waste? The fumes? The ability to leave stuff to settle without being disturbed by kids/pets?
And the last very general thought I will leave you with is, if you are speaking about obtaining platinum, palladium, and rhodium fractions from your scrap gold, the market is quite punitive to those who have smallish amounts. Those Kitco numbers at the bottom of the screen, you're not going to make those kinds of numbers from 3 grams of Pt. You need multiple ounces before most buyers will talk to you. This goes to the "feasibility" discussion.
