What is the best way to sell a record collection?

My dad is looking to down size his record collection down to favorites which he cannot part with. I estimate he has 3500 to 4000 LP and 45’s from the 50’s 60’s and 70’s from blues to classical and everything in between. Does anyone have any ideas how he can go about selling his collection?
Sell a small amount at a time. I would put of for sale choice recordings along with not so choice bundled together. Where are you located I would love to cherry pick this tree. I would not sell as a total collection you will not get full price or even close. Also avoid at all cost record stores they will give you pennies on the dollar. Your better off selling them on Audiogon just a couple at a time and give off a chance to nibble at this treasure.
I sold mine in lots of ten to twenty as Schipo suggests. But, and this a big but, I sold 500 lps not 3500. It was a bit of a pain. Selling 3500 will be a major pain.
Search the archives here as this question comes up monthly.
if you have the time....individually on ebay. otherwise, you buy them from your dad.
Send me an email. I may be interested in buying.
Also send me an email, I may be interested in the whole collection only. I do admit that selling piece by piece will get you a better price, but it may not be worth the hassel.
At a local second-hand store, they think they have a goldmine! Several LPs a on display with prices of $500. $250. $60. And they are all pretty common stuff. I guess someone there is 'crazy' (in more ways than one) about Elvis, the Beatles, and a few other tired retired rock stars.
If they actually HAD something worth anything, they wouldn't even know it...
LPs values are so odd! The market is all over the place. LPs sell here at auction for 10 times what they are worth. (I have a mint 2 eye Miles Davis Kind of Blue, paid $8. for it locally, a reissue in the auctions was way over $30. and still going.)