I have been building on my house for a few years and every now and then I need to hold up long pieces of wood or ceiling boards. I prefer doing these kinds of things when the Wife and family is away, so these are my extra helping hands so to speak. Over the years I have found a simple "T" made from a 38mmX38mm (1 1/2" X 1 1/2")Pine Batten. my "T" is round 500mm or 20" long attached to an 8 foot long batten. I use these then to wedge up or prop up the long item, so I am free to Glue or nail in the work piece above me.
Pictured is this simple tool holding up 7.5meter long Extruded Polystyrene ceiling boards, Else where is foam can be pink or Blue too.