There are many ways to make the vocals upfront.
Doubling is one way only.
Since that is what you are looking for (a doubleing effect)
That is what I'll explain.
It is split into 4 groups.
1. A slapback - were you apply a delay using a single repeat.
Depending on the tempo you arrange the time of the slapback.
this is usualy up to 35ms's and panned center with the vocal.
The effect has a reverbtype kind of sound only cleaner.
2. A larger slapback that makes the vocals sound thick.
ranging from around 35-80'ms. Again both are panned center.
You slowly bring up the delayed track untill you get the sound you want.
3. Doubling effect - use a delay up to 35ms (or less). Pan the lead center but the delay, pan to a different side.
This will give a wide spread and a Stereo alike sound.
4. The triple stereo delay ! - send the lead to TWO delay units.
lead in center, One delay panned right using between 15-45ms delay and one delay panned left using a different amount of delay
also between 15-45ms.
Want even bigger ?!?!!?!? - pitch shift each delayed track by about 5-10 cents ( one +10 the other -10) making sure that the higher pitched track is not dominating the the panned side as well as making sure the shorter delayed track is not dominating as well ( you do this by muting the lead vocal and listening only to the delayed tracks and check out their pull...)
Of course you can simply sing it again.............