Hello here an example showing how to sponge out watercolor in a precise area using masking tape. Left is the original center I applied masking tape and clean it with a sponge right I removed the tape you can see the wiped out area.
It works better with earth colors almost 100 percent and less with very staining colors. If you use it i suggest you to do test on similar paper first like that you won't be sorry or mad about me
to use this technique the paper must be completely dry then you place the tape around where you want to erase and clen it with a soft sponge [ i prefer natural] then blot it with clean tissues do not over do it practice first then remove the masking tape if the paper is delicate let it dry first otherwise do it when it is still wet once again practice before.
This was done over WN watercolour on Arches hp paper. On the left i quickly did the shape of a boat to illustrate you can do any shape.
If you want to rework on the area after a hard treatment you can size it with diluted gum arabic first then let it dry an even polish it with a sooth abrasive they use for cars paint.
This is not new to me but it can be for others
Sorry for spelling mistakes I'm so bad on keyboards