You don't need to do that. Most of us test, feed, and shoot all within 10-15 minutes. There is no need to wait 1/2 hour to shoot. Lantus is a gentler insulin and doesn't onset for a couple hours after the shot. Many give the shot while the cat's head is in the bowl. With the earlier non depot style insulins, it was important to make sure the cat ate so most people waited the 1/2 hour.
You also don't need to pick up food before tests during the cycle. When people are new, we suggest picking up food a couple hours before shot time, so the preshot number is not influenced by food and you know it's safe to shoot. Not such a bit deal if kitty is in high numbers, but is if they are lower. Over time as you gather data and experience, you won't need to lift the food before preshot, once you know how much of a boost Oliver gets by food.