I wouldn't be heaping it on with a spoon. just to start out with...
With some wood types like swamp ash or mahogany, you must expect to do SEVERAL fills before this process is complete. I use a two inch paint brush and apply rather lightly, THEN scrape off excess not actually IN grain and daub excess into the grain pores.
Drying times varies greatly with relatively humidity and temperture. If it's a dry sunny day and you leave the body out in direct sunlight, it may dry in 2-3 hours. If it's cooler/humid at all, it can take more than 24 hours for each fill to dry. If working with swamp ash, I'd ALWAYS recommend at least 24 hours if not longer as the grain is a lot bigger than mahogany and ANYTHING you apply to swamp ash will shrink into the grain with a bit of time
If you don't let it dry COMPLETELY you will just sand most of the filler back out of the grain. Even when fully dry this will happen to some degree, and you MUST do multiple fills.
While this may be a little frustrating, you must be PATIENT, if you want a good professional result.