Fastest to rank to 20, or derank to 20 from 30?

[Hvalpen 251]

Since soldier of misfortune requires some diamond swaparounds(hence losing xp every now and then). Would it be better to rank up to 20, or is is possible to downrank from 30 to 20 after using the warlord glitch? and is it even faster?

[locoporkko 429]

First rank up to level 20 and then make the glitch to rank up to level 30

[TehUberCheezCatz 701]

going normally to 10 then deranking to 20 is faster

[xItsLesterx 1,082]

Cant derank from Warlord glitch Level 30 to 20. You either do the glitch and then 1-20 or 1 to 20 and then derank to do the glitch. 

[colia100 485]

I ranked up to 20 doing all weapons but one along the way (should get you to around 19). Then just boost to 20 and do the warlord glitch.

 

Ranking down to 1 (keep 1 diamond spot free) takes 20 matches of around 2 minutes so about 1 hour in total.

 

This is the fastest way imo.

 

You can also do all weapons alternatively, the change your psn id and do the glitch from there

[urutoraman_k 7]

While doing the manuals, I purposely leave M249 SAW from the Gunner class (requires three diamonds) in preparation for the Warlord Glitch. I completed all the manuals (with an exception of the M249) at level 18. Then I farmed XP until I reached level 20. 
 

Once the Mercenary trophy popped, I reset all diamonds and derank every round, while maintaining three diamonds in Gunner class for the M249. It took around 10+ matches to complete the manuals and then I proceed with Warlord glitch. I was at Rank 7 when I started doing the glitch. Took me around 30 mins because I’m using my alt accounts. 
 

I followed the guide by @dev2610 here:

Hope it helps, and good luck!