We were in exactly the same position a year ago!
As to which questions, it depends whether you're doing the Lincs consortium test only or Caistor Grammar test which is different. We went for both. As I couldn't get a clear understanding of what was required for Caistor, I took the approach that DS needed to be prepared for any question types he could come across. So we worked our way through all 4 Susan Daughtrey books before he started doing practice papers. We probably spent more time doing this than necessary as he got some question types straight away but I still forced him to go through the practice questions
. Then when we started practice papers, we bought as wide a range of VR papers as was practical for him to get through so we could pick up any question types that we'd missed. It all sounds quite laborious when I think back on it but we didn't start until May so we must have got through the SD books reasonably quickly (couple of months I think).
By doing all of that, when he used the NFER papers which cover the Lincs consortium test, he was comfortable with all the question types on them.
I'm sure someone more knowledgeable than me can advise on the actual question types for the Lincs test if that is the only one you're interested in. There are earlier posts on the forum as to which types are required.
This was probably not the most scientific approach but at the end of the day it worked for us. DS needed to pass well to get in as we are out of catchment and he got the school he wanted.
Not sure that this is much help but Good Luck