I don't think I can teach you to paint to awesome levels, but I think I can answer these questions.
bozar wrote:... small bubbles keep showing up and dries on the surface of the mini wish spoils the paintjob.
Yep. Bubbles are a problem when you brush on vallejo surface primer. I find that it helps to use very gentle brush strokes, with the softest brush I have. That means using the expensive kolinsky sable brushes, not synthetic. Also, don't shake the paint pot, use a stirrer instead.
bozar wrote:The other issues I have is two brush blending. [...] Is drying retarder a bad thing when it comes to this kind of blending [?]
Drying retarder is a good thing especially when using a small brush. Also, are you using Vallejo Game Color paints? They've got an additive that causes them to dry very quickly. Can't help you with the moisture problem - I struggle with that myself.
Spot on.