You are correct. If eggs are washed, you cannot waterglass them. They should also be clean meaning no poop, dirt, straw, or other debris on them.
I get 3 gallon food grade buckets & lids from a local bakery for a $1/each. (They have to charge something for them by law here....). I can waterglass up to 5 dozen eggs in these buckets. Because of the nefarious egg eaters in my flock, I don't always get all the eggs I need to waterglass in a few days. Sometimes it can take up to a week for me to get eggs that fit the bill to be waterglassed. As long as your buckets & solution are in a dark, cool place, you can keep the bucket unsealed and add eggs as you get them. I keep an index card taped to the front of my bucket. On this card, I write - date I started adding eggs to the solution, the date I stopped adding eggs to the solution, and the total egg count. For example, if I start a solution and only have 30 eggs, I'll write "30" on the card. As I add more eggs, I will strike out the previous number and write the new number until I reach the total (60 eggs). After I reach my total, I put the lid on and seal the bucket.
I keep my buckets inside a cabinet in a large bookcase in my living room. I chose this spot because it is dark and consistently cool. I also don't waterglass more than I think I'll need. I do 5 dozen eggs on April 1st and another 5 dozen eggs on July 1st. This amount ought to get me through the Dec - Feb lull when egg production drops.