If you engine is reasonably clean, a magnet on an extension works well...
Stubborn ones may require some carb cleaner to get the varnish off.
Otherwise, pull the intake and rocker arms and grab em...Big blocks are nice with no water in the intake.. just a $25 gasket...
Just to add note that back in the day Solder Seal use to make a product called lifter quiet that did a great job of cleaning the lifters in a few hudred miles, eliminating the need to replace them.