The use of aged or composted animals manures is great idea for camellias. Chicken manure will work well for you, just be sure that it is not 'fresh'.

I hope I haven't read your post wrong, JMMadeiros, but did you analize or have your soil analized and found it to be "naturally" quite acidic???? If so, why would you add sulfur , which if added to an already acidic soil, might turn it possibly a bit too acidic? Even acid loving plants must have some limits as to how acid they like their soil. Normally, if a soii is too acid for plants loving sweet soils, or those nearly neutral in pH, a gardener would add lime of dolomitic limestone to sweeten them, but if a soil is acid and you want it acid, you'd add sulfur only if it's just not acid enough. And for plants that like soil a bit on the alkaline side you might add extra limestone. Perhaps you needed your soil just a bit more acid than it already was , so you added the sulfur? Sulfur is naturally acidic!! In general I tend to think of acid lovers, as those plants liking pH's of 5-5.5 to 6.5, but really 6.5 is considered only slightly acid. On the other hand a pH below 5 might be much too acid for some acid loving plants, but I don't know their acid "limits" on the lower end of the acid scale!!

I understood him to say that his soil was 'very little acidic', or not acid.

Try some "Milorganite" which is organic and does well on camellias.