Best way to use frontlines consumables?

So I use a maxed out engineering and inspire but I'm wondering what the best way to use them are
. For some reason, when I try to stop tanks from capping in arty with engineering, I don't see it as making my level increase much, it treats it like just another shot of damage though It says "5 points denied" or something.

Inspire seems more useful when brawling because every shot counts as assist damage but most of the time people are spread out. Are recon and arty strikes any good? How can you use the consumables to level up faster?

Also, do you get more exp for sitting on a cap longer or does it just check if you were on the cap when it was captured and gives you the same exp?

Would appreciate any other advice on leveling up fast in frontlines. I get major every 3 games or so and am usually half way through captain when the game ends.