

I bought new bathroom fittings to replace the old ones before I sell. But when I started removing the old fittings I found holes like this.
I have read that using an epoxy putty is best, so that I can drill a new hole to mount the new fittings. Using a putty seems impractical since the hole is 1cm at the widest point and I can’t fit my fingers in to push the putty into all the areas.
how am I best to go about this and what products would you recommend to get the job done?