reading TVcasualty's comment, I was under the impression that we were talking about bulk substrate that wasn't colonizing rather than grain spawn... I would also not suggest reusing grain spawn. You shouldn't need any of the fancy equipment and unless you are adding an entire syringe worth of spore solution, that shouldn't be the issue. Even if you use an entire syringe, the excess water shouldn't keep it from colonizing....
If we are talking about bags of substrate rather than bags of grain spawn, you should not be injecting the spore solution directly into it. You will not have good or even any results from putting the spore solution directly into a bag of substrate. You need to colonize grain spawn first and then mix the spawn into the substrate...
Just to help be sure we are on the same page...
Grain spawn = hydrated and sterilized grain that we inoculate with either a multi-spore solution or a liquid culture. You can also do grain to grain transfers,
add a wedge from an agar plate, etc...
Substrate = a semi-nutritious medium that is mixed with grain spawn and then fruited. This can include any number of materials including coir,
straw, poo, verm, etc....
casing layer = non-nutritious layer on the surface of the substrate. This layer helps maintain moisture content and creates a
micro-climate that promotes fruiting. I rarely, if ever, use a casing layer for cubes when growing on bulk substrates.
I have never seen much of a benefit or superior results of any kind when applying a casing layer. It is not typically considered necessary with
bulk substrates.
Cubes are really forgiving. You can achieve great results without a flow hood, in temperatures ranging from 67/68F to 76/77F, and with a wide RH range... You can achieve great results without a flowhood, I don't currently have one.
I break up the mycelium in every one of my spawn jars after approximately 15-20% colonization. When shaken, they will colonize more quickly...
To help you figure this out, we need to get some more details. I think there is a disconnect due to your not having the vocab quite right yet... You mention jars but then you also mention adding spore solution to your bags that are not colonizing. If you are using spawn jars, the spore solution would be going into the jar rather than the bag... Only once the jar has been fully colonized will you be mixing it with the substrate you purchased in bags. I would mix the spawn directly into the bag rather than moving it into a different receptacle. I would then roll the top of the bag, clip it, and throw it on the shelf... I use a 1:1 spawn to substrate ratio and get full colonization of the substrate in 2 weeks or less...
I will try to check back before I go home for the day... I do must of my Topia posting while at the office... See if you can clarify your use of the terms as I have mentioned... Describe your spawn type and whether it is in a jar or bag... Describe your substrate and if it is in a jar or a bag... Describe your casing layer...
fyi... you would not be layering a casing layer with anything. The casing layer, which is not needed for bulk substrate with cubensis, is a single layer that sits on the substrate's surface when the substrate is reaching full colonization... The spawn, once fully colonized, gets mixed in with the substrate and then you wait until it has been colonized...
If I was you, I wouldn't worry about casing layers, not right now at least... Just figure out your substrate and your spawn, mix them, and you should have good results