It is best to give this exam when you're fresh out of college. I e seen very few people clearing it while in job. Nevertheless, it's possible. Get dukkis for law papers and any good book for paper 1. More than hours, it depends on how much you can cover.
I cleared this exam in the second year of my LLM back when it wasn't a one year program. I never studied for it and would say it isn't an exam for which you need to 'study.' If you were diligent enough during law school then it is a breeze.
As regards the JRF, it is trickier. Can be a bit hit and miss. I did not get it on my first go, but did on the second. I don't think I can put a finger on anything I changed in terms of my 'preparation.'
I wasn't diligent enough in law school. Plus LLM being only one year now has made it hectic and doesn't leave a lot of time to prepare. Moreover I am already a faculty but I need the JRF to pursue my PhD asap otherwise my promotion is hung up.
I am very well aware of that. Once I get the JRF, I'll start applying for PhD & go full time. I had already cleared NLS, NALSAR & NLUD last year. All 3 of them suggested that I could join without stipend or join after clearing JRF, otherwise it causes a problem in sustaining years long work.
As regards the JRF, it is trickier. Can be a bit hit and miss. I did not get it on my first go, but did on the second. I don't think I can put a finger on anything I changed in terms of my 'preparation.'