Grain 1/4 Pint Pint Lb
Millet 2Tbsp:1Tbsp 1 1/3C:160ml
Milo 2Tbsp:20ml 1 1/3C:200ml
Oats 2Tbsp:20ml 1 1/3C:200ml
Pearled barley 25g:15ml 1lb:270ml
Rye 2Tbsp:20ml 1 1/3C:200ml
RGS 2Tbsp:13ml 1 1/3C:150ml
Wheat 2Tbsp:20ml 1 1/3C:200ml
WBR 25g:17ml 1lb:275ml
WBS 2Tbsp:20ml 1 1/3C:190ml
Millet: a great choice for no prep, cheap and easy to work with. It is 2:1 seed:water by volume, you can let it cool completely in the PC before using.
Milo: Kind of a pain to work with but seems to be good for spawn. Milo benefits from 1tsp of gyp per Qt and a shaking the jar while still hot, after the PC cycle.
Oats: Many love or hate these grains. They are a great price and work really well for hearty spawn. Fairly easy to work with, no gypsum, a warm shake is helpful but not necessary.
Pearled barley: I added this one mostly for edible mycelium TEKs, should be done in bags.
Rye: Another great choice, it is easy to work with, just grain + water, allow to cool in PC.
RGS: Surprisingly easy to work with grain. To measure it is a heavy 2 to a light 1 seed:water ratio by volume. I use RGS for high spawn rate with low nutrition.
Wheat: Another classic, fairly easy to work with, it does benefit from 1tsp gyp per Qt and a warm shake but not absolutely necessary.
Whole Brown Rice (WBR): Another grain I use mostly for edible mycelium TEK. Should use bags for this one.
Wild Bird Seed (WBS): This tends to be dirty and needs rinsing, especially if it has cracked corn in it. It also takes 1tsp gypsum per Qt and must be shaken while hot.
Rinsing: For grains that need rinsing, like WBS, you need cold water, a scale and a strainer. For single jars, add your grains to the jar and weigh it (jar + dried grain). To that # add the weight of the water you will be adding (1ml=1g). The sum will be the final weight of your jar. Rinse with cold water to your heart's content, drain, don't worry about drying. I have a small mesh strainer the fits inside the jars mouth to drain with. Reweigh your jar and top with water til you reach your right weight (jar + dried grain weight + water weight). As an example, if your jar and dry grains weigh 350g and you are adding 200ml water, your jar should weigh 550g after rinsing/draining then topping off. If you normally make multiple jars, consider with the first round weighing them all and taking the average. Just use that average for this and the next runs.

Some final thoughts, no prep will save you tons of time and effort. The grains will not come out evenly hydrated, some will be drier, a few will have burst, some even leave a film in the jar, it is all fine. Of the grains tested, millet, rye and RGS were the easiest to work with then oats, wheat, milo and WBS. Also, maybe anecdotal but grain mixes, seem to work better, two I use a lot are:
I start most of my agar on this grain mix, in a quarter pint jar, add
1 Tbsp oats
1 Tbsp rye
20ml water
PC 90min @15psi
Here it was dumped on MS Starry Night agar

I G2G the quarter pints to these pints then use them to bulk or you could G2G to quarts.
In a pint
2 Tbsp oats
2 Tbsp rye
2 Tbsp millet
2 Tbsp RGS
66ml water
PC 90 min @ 15 psi

W/MS Starry Night

I hope you will try a jar of no prep your next PC cycle and let me know how it works out.
Cheers!
Some conversions
1 1/3 C = 236.59 ml
2 Tbsp = 29.57 ml
1 lb = 454.59 g
Some pics:
Millet
1/4 Pt
(photo coming)
Pt w/Fp+

Qt w/PExAPEU

Milo
1/4 Pt w Fp+

W/MS Starry Night

Pt w/Bell capped subaeruginosa

Qt w/PExAPEU unfortunately I started to shake the jar right before the pic.

Oats
1/4 Pt w MS Starry Night

Oats dumped on Natalensis agar

Pt w/Alutacea

Qt w/Subtropicalis

Pearled barley
Lb w/ Subtropicalis

Rye
1/4 Pt w/Fp+

Pt w/Yellow subaeruginosa

Qt w/PExAPEU

RGS
1/4 Pt w/Pan bisporus

1/2 Pt w/Pan 'Trop Aus'

Pt w/MS Starry Night

Qt w/Pan bisporus

Wheat
1/4 Pt w/MS Starry Night

W/Yellow subaeruginosa

W/Natalensis

Pt w/Gymnopilus purpuratus

Qt w/PExAPEU

WBR
Lb w/Subtropicalis

WBS
1/4 Pt w/PExAPEU

W/Yellow subaeruginosa

W/Subtropicalis

Pt w/W/Yellow subaeruginosa

Qt w/PExAPEU
