For mine, I tried to duplicate Deathproof's technique for the flightsuit which is similar to what ShortFuse did - I can't comment on how to do the vest though. If you haven't seen his thread yet, please check it out because it is a wealth of knowledge for anyone doing ROTJ
DeathProof's ROTJ Fett: BH-32794 . For what wasen't clear in post, he was very kind to answer my questions through some PM's. I did my weathering over a year ago, and I am still planning on going at it again because I don't feel my suit is weathered enough yet. Also, this technique is very time consuming so be patient, but so far I am extremely happy with the results!
**(All credit to Aaron/Deathproof - hopefully I am not butchering his method)**
The basics were this:
Materials:
Paints
Burnt Sienna (jar)(acrylic)
Raw Umber (jar)(acrylic)
Terra Cotta (jar)(acrylic) [I didn't have this on hand when I did mine, but was a colour recommended by Deathproof too)
[I also intend to use a small amount of earthy straw like yellow to to add some colour depth beyond browns as he did- but again, didn't have it on hand then)
Generic Black Paint Spray Can [from the hardware store]
Other
Some kind of Containers/Cups
Disposable Sponges
Spray Bottle filled with water
Clean towels/rag
[I went to the dollar store and picked most of these up for a couple bucks as I just threw them out afterwards]
Charcoal Sticks from an art store
Basically, the technique was to dilute the acrylic colors heavily in containers filled with water, and literally use the sponges to spread the mucky water to match screen references. Wetting the fabric in advance can help to avoid rings and helps the paint spread naturally throughout the fabric. It can be extremely potent depending on how much paint you used, so have a spray bottle and a container filled with clean water on hand to feather out or erase the colour to create gradients across the fabric. When you apply it, the fabric turns out EXTREMELY dark because it is wet from the water, and you will have to wait for it to dry to see how it turned out. You do this over several sessions building up layers with the the different colours to create different tones with a progressively darker gradient towards the ankles. Do your best to use several different tones throughout to make it look realistic. Also, you can use the Charcoal sticks to get some black tones, but should be used very sparingly as they are *very* potent. If you screw up with any of this, be ready to use the water in the spray bottle with the towel to try erase it. Finally, I did a light mist with the black spray can similar to the method's others are mentioning here. Deathproof also advised that sandpaper could help erase things that got too dark, but can be risky to create holes you will have to fix. As always, check screen references.
Hopefully this might help. Good luck!