Delta questions about miles

[MAJPLO]

I've searched and haven't been able to find what I'm looking for. I've searched Delta's site and haven't found it either so I'm hoping someone here has experience and can help.

If I am about 2500 miles short for the tickets I need, can I buy points? buy with existing points and add on the difference with dollars? how long does it take from purchase time to time the miles/points are credited? THANKS Delta experts!

Edited to add...
okay so I got a little more info from a different forum, but I'm still unsure about a couple things.
Can I buy points/miles
Is the miles+cash option a decent deal or is it better to buy three tickets on miles and one full ticket with cash? Any experience here is appreciated.
I'm seeing soemthing about Delta being a partner with Alaska Air. does that mean I can use my Delta points to pay for an Alaska air flight? Or can I earn Delta points when I buy an Alaska Air flight using cash?

 

[lost*in*cyberspace]

This is all explained here:

http://www.delta.com/content/www/en_US/skymiles/program-rules-conditions.html

http://www.delta.com/content/www/en_US/skymiles/earn-miles/earn-miles-with-partners/airlines.html

http://www.delta.com/content/www/en_US/skymiles/use-miles/award-travel/about-award-travel.html

https://www.delta.com/buygftxfer/displayBuyMiles.action

As for what combination of award miles and cash is best, you'll have to work out the costs and decide what is best for you.

 

[sam_gordon]

I've done the miles & cash thing for flights. "Experts" say it's a poor use of miles, I think it depends on the situation/person. Unless things have changed, Delta has three "points" fares, 25K, 37K, and 50K. Well, if your flight doesn't have any more 25K tickets available, but it costs $250, you now have a ticket that requires 25K points. IMO, you're saving money.

 

[OrangeCountyCommuter]

It is better to use miles for the three tickets and pay cash for the 4th. Unless you are buying first class tickets, the miles with cash option means you don't ear any miles on those tickets. So I buy my ticket with cash and use miles for any other tickets.