In a reply to one of your earlier posts I had mentioned that I didn't think you were tapering prednisone correctly, so maybe you should clarify with the specialist how he expects you to use prednisone and taper off it.
Rectal meds could help, but since you have just completed a short treatment on oral prednisone (a much stronger treatment) with only a slight effect, I am not sure that I would expect rectal meds to have much of an immediate effect - but, I suppose it's still worth a try, as you never know how your body will react till you try it. I agree with Tab that maybe your Asacol dosage needs to be increased.
I don't think you should completely avoid prednisone - if it's applied correctly, it could get you into remission and then hopefully the maintenance drugs can keep things under control. I avoided prednisone for a while last year and tried to use only Asacol and rectal meds but things got much worse by doing so.
Being proactive is not really about 'telling' your doctor what medications you want, but more about discussion and questioning your doctor about all the treatment options he sees available to you - with the aim of getting into remission soon. Discuss the pros and cons of each so that you agree on, and completely understand, the next course of action.