I would certainly recommend what Tim has suggested, and that is bleach the areas that are almost impossible to 'hold back' during printing.
For this I favour an iodine bleacher over ferri.
Iodine Bleacher for prints:
iodine 4 gm.
potassium iodine 15 gm.
water to make up to 1 litre.
Remove the brown iodine stain with 30% sodium thiosulphate (hypo) solution.
Wash print well.
This stock solution keeps for years.
You can always dilute the iodine solution further if it is too active.
For lightening small areas I apply using cotton buds. When the desired result is achieved swob the area with the 'hypo', then wash print well. Practice on spare prints.