Here's my typical priming MO: I typically wash whatever I'm priming with dishsoap/water and let it dry for at least a couple days, often a week or more. I spray in a 2-car garage with the garage door open for ventilation, on flattened cardboard or laid-out newspaper. Shake the can for whatever the label says (1 minute or more typically), then spray in short, controlled bursts starting almost off-model, going across the model, and stopping at the edge of/just outside the spray zone; repeat. Depending again on the label, I spray between 6-8" and 10-12" away from the models. I almost always prime multiple models (hello, Tyranid player) at once, keeping them ~4" apart.
The pic at the top of the article is my most recent attempt at the long hoped-for but never-delivered Mycetic Spore wannabe above. Note the pooling, crazing, and spotty coverage; clearly it isn't done, but after noting the pooling and crazing, I stopped. It's a tough item to prime, composed of very slick, almost oily, plastic - this is my second attempt - the first was with Krylon, which covered adequately with only a little pooling, but flaked off from very light handling. Stripped it with Simple Green, and prep washed it very well, ran some fine grain sandpaper over it, and tried a special fine coverage primer (Zinsser BIN Ultimate Stain Blocker) intended to "block water, fire, and smoke stains, sap streaks, and greasy spots, and ideal for 'hard to paint objects' like arts and crafts, wicker, porous wood, spackled areas etc..." The results as you can see, are less than spectacular. The frustrating bit is I was priming an old resin Armorcast Exocrine - and it came out the same way: very heavy pooling in flat/depressions, and either no coverage at all in fine detail areas, or it buried them under a pool or very thick layer. Which makes me believe it isn't the texture/material or material. I let the paint dry and dumped it right into my Simple Green vat where it soaks as I type this.
Honestly debating switching to a light grey primer - but with the bulk of my tyranid 'core' elements painted with a white base, the color value of new units will be noticeably darker. Plus the white base lets me do things with blended acrylics that take multiple layers to achieve on a dark primer. At any rate - if you have any thoughts, ideas, or been able to successfully paint Plasma Hatchers - please drop me a line or two below. Thanks!