Doing the right thing...

... or doing it right now.

While most people outside of remote tropical islands can get easy access to undercoat sprays, if you happen to run out of black, dark green actually makes a very good replacement when doing a large stack of tanks.

Speaking of tropical islands and sprays, the latter have trouble with warm, high-humidity weather, which is remarkably common on the former. You can of course decide to do it anyway, instead of waiting a few months for the "dry" season, and go for the early-mid morning, where the air is the least humid, and the temperatures cool, as long as it's not actually raining, or about to rain. Which is often.

Assuming you've decided to brave the weather conditions, and you're going to have to if you want your minis base-coated this year, the common advice of testing it over some spare sprue remains crucial, if only to find the proper distance to spray, which tends to vary depending on weather conditions. You don't want that rough, grainy finish on your patiently-assembled, expensive, weeks-of-shipping-required minis, do you ?

So, as delicate as it can be to do it right, what happens when you just want to do it right now, ignore the above, and just take a chance in the 20 minutes you have before going to work ?
Well, you could manage the perfect base-coat, with a nice smooth finish, or as I just did earlier, get that dreaded grainy finish, and lots of cursing and swearing.

Fortunately, as long as it's not too bad, and you're working on minis with large flat areas, like say, tanks, a light, gentle sanding with very fine grit will smooth things out nicely, and leave you with a wonderful, flat, ideal base-coat you just want to paint over immediately.
Thank you Tamiya super fine grit !

From left to right, olive drab base coat, with the shade, and after clean-up.

The Sherman horde !