My big ginger boy does this too, it's nothing to do with "spraying", the smell is totally different, in fact it's VILE and almost impossible to get out of upholstery, and duvets as we found to our cost.
We asked our vet and he said his cat does the same thing(!) but there's not a lot that can be done about it except try a change of diet. The substance does come from the cat's anal glands - which normally empty when they do their no. 2's - however, if their faeces tend to be soft, or they have a weak gland "valve" it can leak out involuntarily any time, especially if they've not had much exercise, i.e. eaten, then fallen asleep for hours on end, like ours tends to do. Then if he gets up and stretches, or we pick him up and make a fuss of him, it puts pressure on the gland and it secretes.
Our cat alway knows immediately it's happened and if he's been sitting on my lap he always jumps off me straight away and tries to lick away the evidence (yuk). I feel a bit sorry for him actually - I think he's as ashamed of it as we're appalled! Our vet suggested we try feeding him on some high fibre dried food he sells in his practice, which we did but it made no difference. We try to make sure he exercises regularly by putting him out after he's eaten (and trying to ignore his scratching at the door to come back in after a minute

), and playing with him regularly with a stick and string which gets him jumping about, but apart from that there doesn't seem to be a lot we can do.
I found this link which seems to confirm what my vet said:
http://www.medhelp.org/posts/show/345904
I hope this at least helps you understand what it is, even if you can't cure it!