From my experience in replacing drum brakes, the little bit of fluid you lost is the least of your problems. (Some of the comments above provided some rationale for why some fluid was lost.) The bigger problem is that while the shoes were wearing, the pistons within the wheel cylinders moved out in the bore slightly to compensate for that wear. With new shoes, you've now pushed the pistons back to where they sat originally when the car was new and the shoes were new. Given that brake fluid is pretty corrosive, you now have a good chance of having the surfaces corrode inside the wheel cylinder causing the pistons to freeze up. The result will be that the wheel's brakes will fail to operate properly after a period of time when the corrosion sets in. There are two rather simple solutions, but both, unfortunately, require redoing the brake job. The cheapest solution is to purchase a wheel cylinder rebuilding kit (new seals and internal spring) and a wheel cylinder honing tool (which fits a standard electric drill). You remove the wheel cylinder from the car, take it apart, wipe out the old fluid, mount it to a bench vice, and run the honing tool through the cylinder to smooth out the bore and clean it up. Then rebuild the wheel cylinder with the original pistons and the parts from the rebuilding kit. Neither the kit nor the honing tool are very expernsive. A simplier solution is just to buy new wheel cylinders. They cost more than the rebuilding kits, but are not all that expensive, and this avoids the need to do the work on the cylinder. As noted earlier, to remove the wheel cylinder, you first need to remove the brake shoes, springs, etc. The wheel cylinder itself comes off pretty easily in most cases by removing the hydralic line and two short bolts. Once replaced, and the shoes replaced, just bleed the system to get all of the air out.