The downside of having to 'grind' to get to the next level has a positive side as well, it gives you experience in driving/using an spg.
Know where to set up shop for covering different areas of the map, know where NOT to be because it is a known arty spot where you will get counterbatteried quickly, knowing the favourite spots for artillery means you can find the enemy arty by their tracers when they fire and nuke them instead

Aiming/pre-aiming where your scouts are headed, the lay of the land / hills / dips in terrain, etc., etc.
Crew experience is usually not such a big issue on low tier tanks, it is however a big issue for artillery, even with a fully constricted aiming circle and 100% trained crew you will still miss your intended target sometimes, don't start me on the 50% crews...
Use your firing arc to your advantage: setup shop a bit behind a solid object like a rock or building but not something that is very high => you cannot be fired upon by direct fire from that direction (no LOS) but you can arc your shots up and over and land shells on them ;-)
.........__________>incoming!!<___________
......../..............................................................\
......./................................................................\
....../..................................................................\
you.......[_rock_].........................................enemy tank
Poor attempt at ascii art but the best I can do

When you climb the tree to higher level artillery the bigger your splash damage will be so you do damage even if you miss your shot.
Be sure to announce when and where you will shoot by pressing t before you release your shell so your teammates will know not to get too close or risk getting splashed (friendly fire dmg = you pay in exp and credits after battle on top of pissing of your buddies and assisting the enemy team).