Comfrey / Nettle Tea and Homemade Potash

That's mainly what I use. I have one barrel for nettle tea which I use on my brassicas, leafy greens and sweetcorn as they will really like the extra nitrogen. I also use it for anything that looks like it needs a bit of a boost in nitrogen to get them going. I gave my onions and garlic some a bit earlier in the year and doesn't seem to have done any harm

I have another barrel for the comfrey tea which I use on my potatoes, tomatoes, chilli's, squash, pumpkin, courgettes and strawberrries. In general I wait on using the comfrey till the fruits have set on the plants (i.e mini fruits where the flowers were) as that is when they really want the extra potassium. I also put a comfrey leaf or two in the planting hole if I have enough.

A couple of weeks before planting out I rake in some of fish, blood and bone. For around half my beds I had green manures growing last winter so that was dug in and should hopefully provide enough nutrition to get the plants going. I'm planning to green manure most if not all my beds this year.

I don't have a car so getting large amounts of animal manure is tricky and I like the idea of feeding my plants with purely plant matter. Green manures also have a range of other benefits depending on which ones you go for. I usually choose a mix to get the most benefit.
For example they help to suppress weeds, hold onto nutrients over the winter, some have extensive root systems so help to break up clay and they provide a large amount of organic matter to add to the soil. I left my phacelia to go to flower as it's really pretty and the bees seem to love it. The only real downside is you have to dig them into the soil in early spring and that can sometimes be tricky if it's really wet.

The liquid feeds will provide the plants with nutrients they need quickly as they are in a form the plants can quickly make use of. Although on the other hand they won't last over a long period of time like a slow release fertiliser. Thus it's a good idea to improve your soil as well as just using liquid feeds. This is done by adding organic matter to the soil. In my case I use the previously mentioned green manures and any compost I make. But you could also use well rotted animal manure, seaweed, leaf mould etc

In my opinion creating a healthy soil is the key to vegetable growing.

I generally just water around the base of the plant but plants can also absorb nutrients from the leaves. The thing with spraying the leaves (foliar feeding) is that you need to get the whole plant. Including the underside of the leaves so would really need to use a spray bottle. Also the heavy droplets from a watering can would probably fall off before they got absorbed by the plant. A bit to much faff for me

You could try crimson clover, red clover, mustard or my personal favourite phacelia. They are all pretty fast growing so should do a decent job at suppressing weeds.

If you let it flower Phacelia has flowers that bees and other beneficial insects seem to love (me included!). It will overwinter if the winter isn't really cold, otherwise a really hard frost might kill it and you can just let it rot down naturally over winter.

I believe red clover is a lot more hardy and you can even leave it for a couple of years if you want. Haven't grown it myself though. Crimson clover is a bit like phacelia in that it isn't particularly winter hardy.

Mustard is a brassica so keep that in mind (i.e crop rotation). I've read that it disrupts the eelworms life cycle so stops them building up in the soil, which can damage potato crops. I plant mustard after I have lifted my potatoes.

With all the green manures I chop them down with a pair of shears or a scythe and leave the plant to wilt for a couple of days before I dig it in. Makes it a bit easier.