I have limited experience of breeding bettas (I got to the free swimming fry stage, but then the fry died before they could develop their labyrinth organ properly to breathe air).
The following are important:
1) The female must be small enough for the male to wrap his body around for the spawning embrace. If he can't wrap, they can't breed.
2) As above, conditioning is key, you need to feed them lots of live food.
3) A good method is to sue a big sweetie jar, put the female in that and put it in the tank so the male can see her and start to build a bubble nest (a sure sign of readiness to mate).
4) If he is to build a stable nest he needs floating plants/ a floating mop to hold the nest in place. Also there should be no surface disruption which might break the nest up.
5) For the female's benefit, it's good to provide some plants that she can hide behind in case things go wrong (and she'll need to get away once spawning is finished too, as the male will become very protective of nest and eggs).
6) There are two sure ways to know if the female wants to breed: firstly she will have a white 'egglaying spot', visible as a small white nub in front of the anal fin; secondly her colouring will change so she has vertical bars instead of horizontal stripes. In bettas, horizontal stripes tends to indicate stress, whereas vertical bars means they are in breeding condition.
6) Once you know the female is receptive and the male has built his nest, you can let the female out and remove the jar. Don't worry if the nest breaks up, the male will fix it. It is usual for there to be some violence while the pair test each other, but generally this process will result in breeding.
7) Remove the female after spawning is finished and put her in a tank to recover on her own or with peaceful fishes. The male will guard the nest and fry. Remove him once the fry are freeswimming. The need infusorians/ liquifry/ crushed egg yolk as a first food, and then I guess you could try live brine shrimp/ frozen cyclops.
8) The critical stage for the fry is when they are developing the labyrinth organ (around 1cm long). Some people say there should be no surface agitation, other say there should (to increase diffusion of oxygen into the water, apparently). Either way you MUST have a tight cover glass over the fry rearing tank to maintain the temp of the air above the water the same as the water itself, and also to allow maximum humidity above the water while this organ develops. I found this to be the hardest part of rearing this fish and it was totally gutting to lose all the babies, so be warned!
9) one final thing: male bettas prefer to build bubble nests under things that transmit yellow light, as this mimics the colour passing through the leaves of a particular floating plant in their natural habitat. I did a project on this at school a long time ago comparing yellow, red, green and blue 'leaves' that I made from fastening coloured acetate to petri dish lids and floating them on the water at the same time to allow males to decide where to build. They almost unanimously picked yellow. So if your male isn't keen to build then try making a yellow leaf from something (maybe a yellow margarine tub lid?)
10) on the subject of breeding - I have an excellent book on betta breeding by Walt Maurus, who is the daddy of betta breeding in my eyes. He tells in his book of an longevity experiment in the States where males were kept active every day by chasing them round their tanks. The experiment was still going strong at the time Maurus wrote the book and all the males were 9 years old and still capable of fertilizing eggs, so I'm not sure that LFS fish are 'too old', just not in the best condition i.e. I would still give conditioning them with live food a go. Probably best to buy a younger female though as they will a) be smaller than your male so that the embrace will work and b) be more capable of getting out of his way if things turn nasty.
I had the pleasure once of watching a young plakat-type male desperately trying to form a spawning embrace with a female nearly double his size. Both fish were desperate to breed, but there was no way it was going to work, so in the end the female got bored and swam off!
Hope this helps!
