headache sounds like you didnt wait long enough before smoking with quick light coal. its the carbon monoxide giving you the massive headache that medication cant fix
"not much flavour" - maybe it wasnt even hot enough :O
i really hate quick lights but i have no choice unless we're having a bbq. i'm so desperate to try coconut coal but i cant find any in the uk. i cook my quicklights on a stove when i'm at home and they smoke rally well but dont last long at all.
whatever coal youre using, make sure there are no black spots at all, and then wait for the center to warm up too so theres no hidden blackness inside. it could take a while but it will be worth it