Hello and welcome mcleanbr, to the best DIY's site on the web.
I don't think there will be any easy way to accomplish that task without removing some or all of the decking material. You may have a chance at doing some blown in, if there is no blocking on the joist, but what is on the ground under the deck? bare ground what will need to be covered.
When its all said and done there is usually more said than done