Yep I totally concure with the addition of spurs. Most horses are smart enough to know when you've got them on and when you don't. And when you don't you can kick all day on some of those numb ones and they respond with "la, la, la I CAN'T HEAR YOU!!!!" And of course you still want to ask with your calf first, then tell with you calf, then say HELLO with your spur "I said NOW", sort of deal. Doesn't take them long to figure out that they'd better do it when you ask the first time.
You do have to be conscious to NOT gig him inadvertantly when you're just riding around... keeping your toes pointed forwards and holding on with your thighs and knees rather your calves and leaving your calves loose goes a long way in helping that. Make sure you're sitting on your pockets. Think sit in a chair... riding WP tends to be too up and down for reining.
As far as putting your leg back to cue him... I don't know how far back you're referring.. But you leg should be back slightly behind neutral for a lead departure in order to engage the hips, as the lope needs to come from behind. If he's strung out dog trotting when you ask for the lope, you've not isolated/blocked the inside shoulder and you've not pushed his hip up under himself and slightly to the inside. You have to ride the back end up to the front, but that only works if the neck is functional i.e. not stiff.
Here's a video that shows a lead departure. Not that he not only picks up on his horse to get him soft in the face, but he bumps with his legs to get the horse round in the back, then in the departure the horse's hip comes to the inside in stepping to the lope. http://www.youtube.com/watch?v=fR8TmNvZSjA&feature=related after his first circles and spins, you can see the sequence of his leg position and hand position in asking for the lead departure for the right lead.
If your horse isn't tuned into to you being able to ask for him to get round and supple at the walk he's not going to give it to you at a higher rate of speed. You should be able to pick up on his face and/or bump with your legs at any time and him be tuned in to what you're asking. Also it's very important to never let him just amble around even when you're walking around on him casually. You need to dictate your line and where you're going... helps him stay tuned in. Otherwise they wind up, off in La La Land.