Waterproofing old hootchies, cleaning canteens for NZCF

Hi all, I'm new on this forum but I have been on the Army Rumour Service (ARRSE) for a while. I'm doing a month as a civilian instructor at my cadet unit (CCCU) before I head off to basic training in march,and I'm sorting out the outdoor stores. As such, a couple of problems have arisen. One, most of the hootchies owned by the unit are of the old, yellow-ish DPM type, and as such do not have much in the way of waterproofing qualities, I'm wondering if they can be re-waterproofed and if so, how? As it seems that repairing current stores is a more beneficial route than buying new gear. Two. the unit seems to have hundreds of canteens, some dating from the vietnam or korean wars and as such some are very manky etc. Does anyone know of a reliable method to clean canteens without leaving a residue or lingering chemical taste to any water carried in the canteens in the future?
Cheers

Found this on eHow. Also Ive used baby bottle sterilising tabs for Camelbak gear and they are cost effective way. Maybe if the following doesnt work then the plastic could be so old that it cant be cleaned. As for the hootchies, there are products out there but I havent tried so cant recommend any.

Instructions
1. Empty the canteen completely and place it in a sink.

2. Fill about 1/3 of the canteen with warm tap water, then add the same amount of white vinegar. The exact amount of liquids varies per canteen, and being exact when pouring the liquids into the container is not necessary.

3. Add approximately 1 tbsp. of liquid dish soap.

4. Pour 1/2 cup of baking soda into the canteen, then place the lid onto the canteen immediately, as a chemical reaction occurs that could cause liquids to spill out of the top of the canteen.

5. Shake the canteen to swish the liquids around the inside of the container. Leave the liquids in the canteen for 15 minutes.

6. Empty the canteen and rinse it several times with cool water.

7. Mix 1/2 cup of warm water with 1/2 cup white vinegar inside a separate bowl or container. Dip a clean cloth into the solution, and wipe the outside and cap of the canteen with the moistened cloth.

8. Allow the canteen to air dry completely before putting it away.

I wouldn't even bother about the hootchies, use them to cover any thermal mats you have in store or try and get them exchanged for serviceable ones through the system.