Having scanned over 500 of my 1500 or so slides I can say that it takes time and more time. Some of my slides date back to the late 60's and some had faded and some had a blueish tinge. I edited a number of scans which add to the time. Scan at a high resolution as you will want to enlarge the scans. Remove dust before scanning. My scanner is no longer made but a similar thread is running in Helproom which gives help on scanners.