You remove ALL ? the tie webs on the proposed outside curve.
Do nothing to the inside curve except rip out the now offending rail joiners.
Bend the inside rail (brute force) to the desired curve.
Nail it down.
Then thread rail back thru' the outside curve ties.
Nail it down.
Trim both ends.
Add rail joiners.
not exactly.
you remove the end railjoiners and at least widen all the middle railjoiners enough, that the rails can slip throug.
you remove both rails from the tie webs.
you take one of the (naked) rails and bend it as your wanted curve needs. (if necessary you cut it to length) (inside or outside? as you like. i like to put the inside rail first)
then you cut on one side of the tie webs every connection between ties. (as the tiewebs are straight, it does not matter, which side)
you then slip the already bent rail into the side of the ties, where they are connected with each other, put a railjoiner to one end. (to the right one!)
join your "one-rail curve" at both ends with the other track. if necessary make corrections to the bend of your new curve.
take the other rail and bend it. how much? hold it over the empty railslots and you see, where to bend more, and where less. when bent to fit, cut it, if needed.
take up your curve and slip the second rail into the ties. fix the other railjoiner and reatach the now complete curve to the other track.
push the tiewebs around a bit, till they look evenly distributed. - and now is time to nail it down!
don't be afraid. from the second one on, it will take you less time to do, than it took me to write it.
ps: dont cut both ends! later on you will use the leftover lengths of rail. and one longer piece is better than two shorties.
pps: don't forget, that the inner and the outer rail of a curve have different lengths. (for starters it might be safer, to bend the outer rail first)
ppps: if you follow the above, you'll miss some mistakes i made at the beginning...