Do you have much experience yourself using them?
I was hoping someone had part numbers that would work for intake and exhaust, so I'd only have to buy one size that would work for both but just reading more in to it and visiting the Neway website and doing more reading kinda seems I should just get an appropriate size for each side.
Yes! I use them myself. Done tons of heads.
You need separate cutters for inlet and exhaust..
You can get away with 2 for each seat.
One is double sided 30/45 and the other 60.
They are simple to use but you need to be conscious of what you are doing and keep very light even pressure central to the mandrel.
With new blades just the weight of the cutter is enough.
Put engineers blue or black marker pen on the seat before the first 45 cut.
A light turn of the cutter barely touching the seat will reveal if the seat is off centre to the guide.
Do not let the cutter follow the original cut unless it is already running true.
The latter is more applicable when cutting seats from newly fitted guides.
With the 45 you only need enough cut to clean the seat and as Scirocco already stated a couple of turns is all it may take.