Hi,
If you set the 1000 litre tank up on blocks, you can then feed your trolley tank under gravity. With the Schutz IBC 1000 litre tanks, we take the spigot off the valve, cut off the bend, and hammer ordinary 1 1/2" solvent weld waste pipe through from the valve end of the straight bit of spigot remaining. It's a tight fit, and doesn't leak. You can then carry on from there in inexpensive solvent plumbing waste fittings. Hope this helps.
Yours, Andrew