Painting fairing thundercat

[rhys1005]

The tail tidy/under tail whatever it's called on my thundercat had a lot of cracks in the paint and looked a bit of a mess. After seeing it my dad offered to spray it for me free of charge (yay). He sanded it down with an electric sander and took it down to the fiber glass (seemed a bit un nessesaryb)leaving some parts thick and other parts really thin so i bought some filler to even it all out which seemed to work at first but after i could see pin holes in some places.
I went out and bought some filler primer and gave it a few coats then sanded it down a bit to even it out again, but as soon as i did the holes just re appeared and the surface is still really rough and has quite a few visible marks.

Anyway i've just gone out and bought some more filler and filler primer to try and fill the holes and to get it smooth. Does anyone have any tips? I cant see it being as smooth as the rest of the fairings now and at the moment it looks a bit of a mess. I asked my dad as i don't have a clue with anything like this and he said it will be fine but he also said that it would only take a day and it's been three days.. I asked about laquer as the paint he has is a dull white he used on his car but he said not to bother?

I need someone to give me some tips/advice being 18 i have pretty much no experience with resprays and im getting the impression he doesn't know what he's doing and is just blagging it (he does this a lot) leaving me out of pocket and stuck with no tail tidy.

Thanks