If they are vintage brushes, best to separate them into groups fit for a certain car.
Aurora tjet brushes are copper and flat on both sides.
Tough Ones/ Wild Ones are silver and flat on both sides.
Afx non-mag (like JL Tough Ones) have a notch on one side, and are domed on the other.
Afx M/T (like X-Tractions) are flat on one end and have a nipple on the other.
To avoid any problems use brushes intended for that car. If you are short, many online stores (SCJ, Jag Hobbies, Bud's HO, and others) have plenty of each.