NCSS takes a long time. Indeed that is the whole basis of the 'solution', that it is very gradual and slow.
Another, much easier no cry sleep solution would be dummy + bouncy chair
(but that advise really wouldn't sell many Pantley books.)
You don't have to not breastfeed to get your baby sleeping. Sounds like over tiredness to me, rather than being anything to do with feeding.
"I need to establish a routine"
OK. My favoured routine is EASY: Eat, Activity, Sleep, You time
It seperates feeding and sleeping so that feeding happens when baby wakes, not when he goes to sleep. It also ensures regular naps throughout the day, regular feeds and gives structure and routine in a baby-lead way.
From 3 months to 5 months I was on a 2 to 2 1/2 hourly EASY routine, with one hour between feeding and sleeping. You work out an EASY structure that works for you then just repeat, repeat, repeat through the day. So mine went:
Feed - takes about 15 minutes
Activity - until tired signs or until 1 hour after feed (whichever comes first)
Sleep - Bouncy chair, dummy... bounce, bounce, bounce into sleep oblivion, reinserting dummy as needed.
You time - that involves me sitting on sofa MNing and watching TV while bouncing the chair
So I would be aiming for 45 minute nap (to complete the 2 hour routine) and would keep bouncing baby back to sleep at any wake ups until she has had at least 45 minutes.
Once 2 hours has passed from the initial feed, stop bouncing and wait for baby to naturally wake up (which might be another half hour, or even longer, or might not). The start again with the "E" of EASY, so that you are back to feed. then just keep on repeating the whole process over and over through the daytime.
This whole process therefore means baby has 45 minutes sleep in every 2 hours and also has 1 full feed every 2 hours through the daytime. That's my EASY routine though - the one that suits your baby might be different. That's the joy of a baby lead routine. Structured, but also flexible.