How To Smudge And Not Lose The Color?

[abrogard]

I am trying to correct a photo where there was too much bright white reflecting off spectacles.

 So I've been smudging the dark frames over into the white area.

 Works quite well but I notice that over time I lose the color.  That's the way smudging works, I guess.  It takes the first pixels and mixes them with the next I think, doesn't it,  so they get 'diluted'.

 Any simple way I can stop or slow down this dilution and persist with a color for a while?

 You can see here how far I've got...   Bit messy but it only has to be a tiny visa pic..

 I'm not doing well trying to insert the pic... perhaps I'll insert a link...

https://imgur.com/T0BNc5U