I just opened up my MG Wing Zero and noticed that some the feathers of the wing is made of rubber. Can these feathers be painted/sprayed using Tamiya spray cans?

just look at the base color of the decal! If it is Green then it is water one, if it is those see through plastics one then is dried transfer!
I dun have a Wing Gundam but i would like to have the W Gundam Feathers for modding!

bro asuk, mind telling me wat kind of spray can u use which hv glossy pearl? izit Mr. Hobby?

i thought of buying it to use on unicorn next year 

well, you've just encountered the biggest pain when it comes to painting with acrylics

This' also the reason why its a good idea to prime your model first before painting, so that its easier for the paint to stick. Try getting yourself a can of the Mr Surfacer to prime your kit first.

Then, the other thing to remember about acrylic painting is that you'll need to apply the paint in multiple thin coats. The first coat is to just cover the piece that you're painting. It don't matter if you can see through the first coat to the plastic or the primer under it, as you'll fix that up on the 2nd coat.

Basically, its all about patience lar

And for the small parts, use a small brush lor

well for that problem u need to control your painting skill which for my experince the 1st layer paint  dissolve due to too much tinner  or bad mix tinner retarted ratio or hand brush stroke on the same area too many time. So to my best solution are after primer it and painted 1st layer (Mix tinner retarder = ratio 1:3) then when come painting 2 layer u need to control your tinner paint (just put ratio 1:1 only) . For me  after painting 1st layer gentlely then i leave it for 10 min for it to dry then paint 2 layer gentlely again then 3th layer time will cover all the surface without having the bottom layer dissolve.

Most important thing is do not brush paint same area more than 5 stroke (must leave it dry for 10 min then only continue) that will surely avoid this problem .

Hope that will help you