Thanks folks, I too have bought a large 4 litre container and will try the warming with a bowl of hot water. My garage is some distance from my house and the idea of finding a solution (no pun intended) that reduced the likelihood of it all cooling before I got my car out to spray it, made me look into other possibilities.
Thanks Guy, I did see this, but liked the idea of using a garden sprayer or similar with a long lance so I can get right into the grot traps and up behind the fuel tank.