I bought a new Shimano Vanford and will be spooling it up for the first time. I will be putting a mono backing down and then finish it off with 15lb 832 braid. I can put it on easily enough but I have read some on here talking about after spooling the reel taking the spool off and letting it sit in warm water for a bit. Is this just an old wife's tale or does it really do some good? If so warm water and not hot? Let it sit in there about how long? Are there any parts or pieces of the spool that should not be exposed to sitting in water that long?

The warm water technique is for spooling it with FC or mono.  Don’t worry about it with braid

If you are using stiff mono the warm water trick helps. It forms the line to the spool.  On braid it is not necessary and actually a waste of time.

That probably pertains more to going “full spool”. Since it appears you’re using the mono as backing, I see absolutely no need to waste that time. Winter is over, lol. 
 

I wouldn’t even do that if I full spooled mono and I use mono a lot and I go full spool. I have not come across any mono that would ever make me consider trying that. Save yourself the time and what I perceive, the trouble. 

Nope.

 

Nothing like putting memory on your line right out of the box?.  As has been said with braid not necessary.  I have never used the warm water method.  I will spool a spinning reel and then open the bail and walk out as much line as I can.  Then just reel it back on the spool pinching it with my fingers to give it some resistance.  

No warm water - run it through a rag dampened with KVD L&L as I'm spooling.

I'm not soaking any reel or reel part, like the spool which includes the drag assy, in water.  While some may argue with this logic, I see no reason to do it and there is risk of damage involved.  Why take it when there is no necessity.

 

I was at one time advised to soak the fly reel attached to the rod in a bucket of fresh water after using it in salt.  I refused (and just rinsed with a hose) and had no problems.  Others who followed the advice were not so fortunate.  One $600 fly reel had to be rebuilt and a big name fly rod had its grip loosen.

If you want to "soak the line", you're better off placing the spool of fresh line in hot water, not the reel spool. With a bulk spool, it's not really necessary. With a filler spool (which is much larger in diameter), it can help to reduce the memory of that huge spool to the one on the reel. 

 

Regardless, no need for braid!