Warped steel in sand blasting is a combination of heat and air pressure, if you've bought a kit it sounds like it's a baby, so you shouldn't be too fussed about excessive heat.
I used garnett on my 1000 and then recycled the old stuff off the floor and this produced a much better more delicate cut (although is was much more dusty).
With your panels avoid the large expanses that are somewhat unsupported (bonnet for example) but like I said if you have a small kit you should be okay with the pressure & heat.
If you do have a small kit have the paint gun at the ready and blast an area then throw some primer on to seal the steel. Smaller kits mean you are blasting longer, meaning your steel is exposed for longer. Big kits will blast a panel in a matter of seconds so I actaully blasted most of the car then primed.
How big is the kit you got? If it's a big bastard then ignore most of what I said. Hit the panels on a decent angle so as not to direct the full pressure perpendicular to the surface of the panel.
Make sure your pressures are good and that your nozzle is correct for the job, like I said I reccomend Garnet which is an orangey reddish maybe even pinkish colour.
Keep in mind if you use a very course grain you will pit the steel meaning your calculations for paint usage will go out the window as you have more surface area to cover and you also have to build the primer base so as it covers the pitted steel. Buy some high solids primer in bulk and be prepared to do lots of rubbing back.
Soda blasting is much more delicate and would therefore attract less paint prep work, compared to grit blast.
Here are some pictures, let me know if you want me to take them off after you've seen them, afterall it's your build thread not mine

