I don't know all suggested methods. But i can report about KfW credits. I can tell you it needs a lot of time and also some thousand euro in advance. If you request a low interest rate credit (like 2-3.5%) for small business there is the KfW credit. I made something like this and i can report you.
The system is as that: your bank is giving you a normal credit, but instead of a high personal safety (like a house) the public government can give you the safety deposit. So, your Bundesland is taking the risk of loss of 80% in first instance. So, if you get bankrupt they pay first, and then they want the money back from you. So the final bank risk is only 20% and this decreases the interest rate. But this service is not for free. First, the hole procedure costs some fee and it may happen that they reject although you paid the money, then you need a life insurance in the height of the credit and then they want to have 1% per year as risk fee. Additionally the bank and the KfW is often requiring papers of signed by your tax consultant, which costs extra money. Finally the complete procedure can take 6 month - 2 years and is only interesting for bigger volumes of at least 50.000€
Not mention was the crowed funding platform Kickstarter. You can also think about it.
Anyway, liquidity is a basic problem of all companies. The best approach to fix the liquidity problem is to ask the companies that deliver you, that you can pay them later. Additionally ask private people for credit is also an option. This avoids the problem of being bankrupt, if you pay your rate a bit to late during a bad time.
Finally, i think a better approach is to check how you can optimize your startup, that you need money for investments only, not to finance existing structures.