Homebrew PCBs

I've started fiddeling around with photoresist spray and developing it 
using caustic soda, and have a few questions as the board is still not 
coming out 100%


1) How thick should the photo resist be sprayed on. After I've sprayed 
it on and its dried you can clearly see the purple film - there's no 
gaps. 

2) After you put the board in CS - how do you know when to take it 
out? I can see the tracks clearly but the pcb is still have a layer of 
the purple stuff on it. Should the purple film vanish completly 
(except for on the tracks) 

3) Which is a better etchent to use - Ferric Chloride (mine works 
really slowly even when heated up - like 30-40mins) or Hydrochloric 
Acid+Hydrogen Peroxide 

I've done another board (etched) and the top half of it is perfect - 
nice clear tracks. But on the bottom half none of it is etched. If I 
leave it in too long it starts to eat away the tracks, but still 
doesnt touch the bottom section? Does this sound like too thick spray?