When I restored my 1960 3HP B&S fitted to a water pump I found removing the valves quite easy. Compress the collar and spring and pull out the little pin; re-assembly was quite easy too.
The 1976 engine I am re-building however, has no pins but, the collar has an elongated hole. I am sure there is a good engineering reason why B&S changed the design but, as for removing them, they’re a nightmare ! The B&S valve spring compressor is next to useless and the whole process is slow and frustrating.
I’m sure the people who design these things never have to work on them. Having worked in Industry for some years I have found some designers surprisingly lacking in common sense.