Skills going red/downgrading and recovering them

How much does it take, as it seems no matter how I try, except under rare circumstances, it will just chew threw my XP and leave me with no XP and a skill that’s still not out of red (throwing 7 for example). I also haven’t had a skill downgrade I think, they’ll just sit at red and won’t go down. atm it would cost less xp to let them downgrade and level them back up vs trying to keep dumping XP until it goes ‘over’ 0%.

I’m fairly sure that when a skill is red, it still has a normal value. It is just below the skill number it was at before.

IE if you have skill 7 (23%) and it rusts down to 6 (99%) it will display 7 (00%) until it reaches 5 (99%), at which point it will display 6 (00%). There is no difference in skill gain rate or experience expenditure- it simply fudges the display.