You can also do this:
“Get the chain onto the biggest cogs on both the front and rear mechs (to create tension). Turn the crank to get the QR link at the 3 o’ clock position on the front cog; hold it there with finger pressure. From the bottom of the cog take up one link’s worth of slack in the chain and advance it anti-clockwise, up and round, until it is adjacent to the QR link at the 3 o clock position. If you’ve done it correctly the QR link and the link next to it (below it) should be pointing outwards in a ‘V’ shape; hold them both in that position by applying finger pressure to the links on either side. Then simply strike the apex of the ‘V’ with a small hammer or similar (obviously don’t be stupid about it) and the QR link will just come straight off.
“
Or use a bit of old brake or gear cable.