Hi OP
I have had some of my windows refurbed professionally with a similar process to the rediseals link above.
The main feature is that the windows run on some draft proofing pile (like the stuff that insulates modern double glazed windows) rather than a wood to wood interface which is bound to wear and leave gaps.
They rattle less and have less obvious draught through them which is good.
However thinking that it is a long term solution is probably not right as some of my frames have rotted under the new paint and I think I am going to have to replace them all with modern UPVC sash units soon.
I would have thought that doing it yourself would be difficult, but if you have the skills patience and time, very rewarding.
Hopt this helps
Al.
However it cost me a lot (front elevation only around 2k for 4 rooms with large windows, a few years ago)