I jointly own a property (50/50) with my brother. I am thinking of selling my share to my brother.

I am also married so to maximise our capital gains allowances on me selling to my brother I was wondering if I could simply gift my wife an assignment of beneficial interest in the property OR would I have to gift her 25% of the property ( 50% of my share) by recording a transfer of 25% ownership with the land registry before we then sold to my brother? Also, if I did this would my wife be liable to stamp duty on the 25% share that was transferred into her name?  I am just trying to work out the best way to use both myself and my wife's capital gains allowances when I sell the 50% share to my brother.