I use sand. Good job getting some for the cories mine love the tankful of it.
What I would recommend is to first turn off your filter. If that sand stirrs up while you're messing around it can make your filter have a fit.
Once your filter is off, i'd probably put the sand you want in a plastic baggy and using your hand bring it to the bottom of the tank. Gently dump it where you want. I find that sand CAN be messy but it doesnt have to be. Just control where it goes.
Best of luck.
PS if you don't get sand all over your house, then you're less of an idiot than me
*wipes sand off sock.*