My cut-off temperature for regular flooding is -8'C or 17.6'F. Anything above this I find the water pools and you tend to get more shale ice than solid ice. My preferred temperature for regular flooding is -10'C/14'F or colder.
For the spot treatments, don't pour the whole bucket in one spot at one time. Use your judgement, pour slowly and watch the warm water find the air pockets. Once all the bubbles stop and all the holes are filled, move to the next section.