Easiest and most cost effective solution is to use the Sawed-Off Shotgun which becomes available to you when you unlock the ability to play as Trevor and complete his first mission Mr Phillips.
The gun is only $300 to buy, and as it has no proper attachments you only need to buy one tint to unlock it. Cheapest tint is the Army Tint at $100 bringing the total to only $400.
The achievement unlocked after I applied the tint and exited the menu.