For this project I used rubbing alcohol, waproo stripper and waproo sprayon colour change. I will also need a sealant I will update with that process later.
First I cleaned the bag with the rubbing alcohol, then used the stripper to thoroughly clean the bag paying particular attention to the parts with very cracked surface. It is a bit scary seeing the colour flaking off but it is important to get any loose colour off the surface to make sure the new colour adheres well. Then use masking tape to cover anything you don't want painted like hardware and internals if you want to leave them as is.
If you don't want to end up with fingers like this I recommend gloves...or just keep enough stripper to wash your hands with after.
When the stripper is dry the fun starts. Shake the sprayon colour well and then in light even strokes coat the bag paying particular attention to seams and crevices.
I also painted the internals by pulling them inside out.
I gave a second touch up coat when the first was dry and have enough paint left for any future touch ups if need be.
I need to seal the bag now as it is transferring colour to my hands when I touch it. A good sealant will fix this and I will let you know which one I decide to use.