I do not believe that the formula has changed. I think it’s just a case of perhaps the bag being more convenient than a box - I have the boxed set and wish I had the bagged one now to save space.
I can’t say I have any techniques. I just play with them until I get desired results. One thing is that I find they need to be really sharp to have good control and thus found a good quality pencil sharpener. As Darren mentioned, they do seem to work better on a matt surface, but I’ve tried them on a glossy surface and they can work with a bit more pressure. They can be frustrating at times but that’s more my lack of experience with them I think. I too struggled at first and only got faint marks or none at all, but once I sharpened them found this became less of a problem It just takes playing around and finding the right pressure to apply. And again, keeping them sharp.
For chipping I find them much easier to control then paint. I apply dots in random fashion around areas that I want lots of tiny chips and also use them to apply chipping effects on edges of things like fenders and hatches. I still use paint and sponge techniques as well, but the pencils provide a good “in-between” method. I also find them good for putting on longitudinal surface scratches (i.e. in a color slightly lighter then base paint) on things like schurzen or such.
For metallic effects I find the pencils to be of medium hardness; I have graphite sticks that are hard and soft, so the pencils again provide something in between. I’ve used the aluminum to provide some very fine highlights on MG barrels that have been painted black and then rubbed with graphite. Again, this is simply taking a sharpened pencil and gently rubbing the side of it on edges of the barrel.
I tried applying woodgrain on the base of a wooden box and also wood chips on the antenna trough of a Panzer II. Not as happy with that but I think that perhaps is more to do with the fact that the base color is too light to see the effect.
One thing that people don’t realize is you can use these wet. Dip the tip of the pencil in water to make it slightly damp and it goes on easier and produces different effects. You can also take a damp brush after applying the pencil to blend it. I’ve only tried this once with a rust tone to blend the edge and it seemed to work ok. Need to experiment with this more.
The AK book does have some good ideas on using them and it’s only about $12USD so not a huge investment. Many other AK books have modelers using them in their articles as well, and I believe I read one article where the author only used the pencils (except for the base paint) to finish the model to see what they can do. I thought the results were as good as using all the other techiques.
They can be and are (at least to me) one more tool to use for finishing. Again, they won’t replace other tools and techniques, but simply add to them. I find that they are a lot easier for me to control then a fine paint brush so that is why I want to continue working with them.
I would post a few pictures, but I am unfortunately away from home for 10 days so am not able to until then.