I was thinking I can just sand down to the white layer underneath using sanding blocks and then spray it with my paint mixed in a can? Let me know guys, thanks.

 

Better off using a DA sander on that. You'll be there all day with a block. You wanna take all that off, unless you want the same thing to happen in a short while.

 

Is it really gonna take that much longer with a block? What if I use a coarse grit?

 

I really don't understand why everyone thinks a block is the trick for everything. When sanding filler or final sanding,yes a block is what you need but in your case hit that bitch with a DA and go from there. 80 might be a little much since you really don't have much experience. I would say start with 120 and then work your way up. Just keep checking to see how far you need to go down. You wanna get all of that off though.