[dsraven]

if you bought the supplies from anautobody suppies dealer they probably have a shaker but sometimes you gotta jog their memory on getting your purchase shaken. if they dont have a shaker you may be able to get a local house paint supplier to shake it for you, they usually don't like to shake an opened can though.
they say the epoxy part will last for several years if kept in a warm environment but the catalyst part is usually not that long lasting they say. darker color is ok, they say, as long as it is not thick. it seems like if it was bought recently and kept in the proper environment and not frozen then it should have been no problem if mixed correctly. personally i would have doubts if the catalyst was dark. maybe call and ask the supplier. the base coat is not where you wanna skinp on quality, it would be like skimping on the foundation of the new house.

after sandblasting there can be quite a profile on the surface of the steel. it is recommended to sand that down before coating, otherwise the high spots of steel in that profile can be exposed above the new coating. in that case a flash rust could show and possibly change the color. what I do is clean the surface as good as possible to remove contaminants that could be pushed into the surafce by blasting, then sand blast blast, grind off any newfound bondo so it is bare metal everywhere-bondo is not a sealer so moisture can get through it and start rust under the bondo, then sand the blasting profile down smooth-a rag dragged across the surface doesn't catch on the profile, wipe down with silicone wax and grease remover-use lots on the rag and use a good clean rag to wipe it off. use several cloths when wiping so you don't just take contaminants from one spot and move them to another. I have learned to use a quality paper towelling for this as home rags can be holding fabric softeners etc, which will leave streak marks and pinholes in the coating, let sit to flash the solvents off, then spray the coating. I don't worry too much about using a tack cloth when doing epoxy because it will get sanded again anyway. you will likely need a few coats so watch the recoat time but don't lay too much on or the outer layer will seal the inner layers in and they won't be able to flash their solvents off. this will mean the outer layer will dry but the inner layer will flash it's solvents under the outer layer and leave bubbles in the outer layer-known as solvent pop.
there are a few sites that will show you how to set up your paint gun for a proper spray pattern and flow, some of which can come down to air line and quick connect fitting size and flow rates. if you end up with a dry pattern it could, I suppose, allow for different colors like that shown in your pics. possibly some spots where the product dried in the air, more or less, before it contacted the surface. that would leave a pebbly surface.
all things being done right, i would lean towards a bad product. possibly not the suppliers fault at the dealer end. could be his supplier?
what have you got for a gun, regulator, drier, seperator, etc? and, most important, breathing protection?