When I started collecting (2nd time around) worldwide and had 6 albums of stamps to remove and sort, I found that glassine envelopes worked very well. I bought a pack of 100 3x5, thinking I would never use all those. Well, I ended up getting a second pack, and now will likely get a third pretty soon. My initial sort was by country, by time period (1840-1940, 1940-1950, 1950-1955). Also, I use a miscellaneous envelope for each letter or group of alpha letters to hold stamps from countries where I have few samples.
Along with this, a copy of Linn's Stamp Finder ($10) has been a great help, and as I only collect WW thru 1955, I found a set of Scotts 1955 edition catalog (2 vol) for about $30 on
ebay. Once you get the hang of it, they are invaluable!