I'm sure this isn't the 'legit-legit' way to play it, but it's fun to play it like 
this for me, at least.
And as far as strumming goes, I usually just go -down- once for the verses, then -
down--down- for the chorus, but whatever works for you, really.

STANDARD TUNING (capo 1)

(("Now usually I don't do this, but uh, go head on and break 'em off with a lil' 
bit of a preview of the remix"))

VERSE 1
            G
Now I ain't tryin' to be rude,
               C                     Bm
But hey pretty girl, I'm feelin' you,
            Am
The way you do the things you do,
              D7
Reminds me of my Lexus-Coup
               G
That's why I'm all up in yo' grill,
                  C          Bm
Tryin' to get you to a hotel,
              Am
You must be a football coach,
            D7
The way you got me playin' the field

PRE-CHORUS
               G
So gimme' that toot-toot,
                    C        Bm
Lemme give you that beep-beep
            Am
Runnin' her hands through my 'fro,
         D7
Bouncin' on 24's
           D7
While they say on the radio

CHORUS
           G
It's the remix to Ignition
       C             Bm
Hot 'n fresh out the kitchen
     Am
Mama rollin' that body,
          D7
Got every man in here wishin',
        G
Sippin' on Coke and rum,
          C                Bm
I'm like, so what I'm drunk
         Am
It's the freakin' weekend, 
                  D7
Baby I'm about to have me some fun, singin'
G                      C              Bm
 Bounce-bounce, bounce-bounce, bounce-bounce, bounce,
Am                    D7
 Bounce-bounce, bounce...

VERSE 2
               G
Now it's like "Murder She Wrote"
       C                       Bm
Once I get you out 'dem clothes,
     Am
Privacy is on the door,
                   D7
But still they can hear you screamin' "more!",
         G
Girl I'm feelin' what'cha feelin,
        C                 Bm
No more hopin' and wishin',
             Am
I'm about to take my key,
                D7
And stick it in the ignition,

(PRE-CHORUS REPREATS)

(CHORUS REPEATS)

BRIDGE
G                      C           Bm
Crystal poppin' in the stretch navigator,
       Am                         D7
We got food everywhere, as if the party was catered,
       G
We got fellas to my left,
C             Bm
Honnies on my right,
   Am                            D7
We put 'em both together, we got drinkin' all night
    G                       C          Bm
And after the show it's the after party
    Am                        D7
And after the party, it's the hotel lobby
     G                        C              Bm
And 'round about 4, you gotta clear the lobby
     Am                        D7
Then take it to your room and **** somebody

(PRE-CHORUS REPEATS)

(CHORUS REPEATS)

OUTRO
G
 We be off in this Jeep
C        Bm        Am
 Foggin' windows up 
             D7
Blastin' the radio
       G
In the back of my truck
         G
Bouncin' up and down
          C         Bm
Stroke it round and round
       Am
To the remix,
        D7              G
We just thuggin' it out.