first get it all stripped and wait for it to dry. You need some RIT denim blue dye. Grab a jug about as tall and wide as your hand, or about that same capacity and fill it nearly to the top, leaving about a pinky finger distance to the top of the jug. Fill it with very hot water, not from a kettle, or boiling water. But as hot as the regular sink tap will go (should be too hot to touch, still). Then with the same hot water (under the tap this is) wet the bleached/stripped out blazer thoroughly and then squeeze it out dry (while still leaving it damp) and put it aside. Grab some salt (just regular table stuff) and add it to the jug. I usually just shake my shaker over it for about 3 seconds, just a little decent pinch of salt. Then grab a little spoon (teaspoon is it, I can't remember?) and nearly fill the whole thing up with some of the dye. Don't lump it on and make a big mound of it, but just 4/5ths of one teaspoon, flat looking, maybe the tiniest raised portion on it, and throw that into the big jug. Stir it up for about 30 seconds, then grab your damp blazer and throw it in. Just keep agitating it with the spoon under the water, and stirring it. About 15-20 mins, or sometimes up to an hour. Push it under the water, stir etc just keep it moving. The dye will recommend you dye it 3 shades darker than you want it to be in the end. This is total BS, you'll have to get it literally about 10 shades darker, they dry up very light if you don't do them dark. I get mine REALLY dark blue, almost a black shade at a quick glance. Then you take it out and turn the tap on to get some hot water (quite hot, but you should still be able to hold your hand under it) and start very gently just holding it and washing the dye out under there. Gradually get it warmer, and then to just cold water (about 10-15 seconds from when you start washing it until you're finished). Just throw it under there and gently add in the cold over that period. Water should be running clear by that time, then just give it a very delicate squish in your hand to get the excess water out and place it on a newspaper stack to dry. Not in sunlight, and not forced drying. Just sit it inside somewhere in ambient temp and wait a few hours or overnight for it to dry. Voila, it will lighten up to the perfect purplish, lightish blue, greyish color
It's really just trial and error but to get the best spot on colour, I've found you have to dye it with the RIT, wait for it to dry, then dye it again with Dylon to get the exact movie colour. Both denim blues from each brand
