Coincidentally, I will be burning about a half dozen brush piles I have scattered around my property in the next few days.
They vary in size. I started today with the smallest one. I have only a couple that will require tractor work as they burn or at some point later when they have burned down. I won't be 'adding' fuel to the piles as the OP is wanting to do, but pushing the ends in IF they have not already fully burned.
Generally...the piles burn quite well without manipulation. IF control is a factor I will light the piles such that they burn upwind.
I douse the piles with old engine oil (saved back). Spray that with some diesel fuel from a hand pumped garden sprayer. I then use my back-pack propane torch to initiate the flame and force feed the pile with oxygen using a leaf blower. It gets the pile burning very hot, very quickly.
I keep nothing more than a rake at hand to put out small areas of grass right around the base of the pile. I don't burn in dry conditions and I clear the area around the pile prior to lighting it. Have never had a fire come anywhere close to getting out of control.
View attachment 90755