Replace valve seals without taking off head

It has been posted before but can someone give me the run down on exactly what needs to be removed to replace the valve seals. Looks like some head bolts need to come out and the cams removed. Rocker arms removed? Best tool for the job?
I also read a previous post that the oil problem was a stuck scraper ring. The front exhaust ports and the 4 inlet ports are good but the rear exhaust ports shows signs of oil. Adding to this that the bike had filthy oil and was only run for 10 km in the last year is this likely to be normal leak past the seals on two cylinders? I have wiped the valve stems in the exhaust ports clean and wait to see if any oil returns to them over the next few days. If so = stem seals.

I bought a tool from a guy in the US to do this job,fantastic bit of kit that required cam and rocker removal.
I then realised only four bolts were holding the head on.
For the cost of a gasket I opted to remove the head and do a proper decoke.
Could have bought 10 gaskets for the cost of the tool,every day is a school day

Thanks for that Bif. I wondered whether there might be a gasket leak etc after removing so many bolts. If you could just remove the cams like on an inline four without removing some head bolts it would probably be ok to do this.

Hey Downunder,
as you say the bike has only run 10km in the past year, had you thought of just ensuring you had sufficient oil, and then giving the bike a decent thrashing and getting it hot?
If it roadworthy and reliable, this is probably the best way of working out if it is just gummed up oil rings, which usually come good when the bike is ridden hard and up to normal operating temp.
Just a thought, I’d rather be riding than removing motor just to replace valve stem seals. Over the years I have rebuilt motor with new rings and oil seals- motor does not blow smoke, but always uses some oil when ridden hard. Plugs show no signs of oil burning. I`ve just had to accept that this motor has a thirst for a little oil, and have known other VF owners who reached the same conclusion.