Hi. This is a good question that a lot of startup entrepreneurs face and thanks for asking.
One first needs to determine if there is a shareholder agreement in place between the existing shareholders, and if so, this may contain clauses ( called "pre-emptives" or first right of refusal) which require you to offer the 10% to your team first before offering it to third parties. I need to understand your situation first, and why you are looking to reduce your shareholding - I assume it is to reduce your risk.
You be looking at the following options:
1) Sell it to your staff. You can draw up a simple sale agreement detailing the terms of the purchase. In the US, you can find a template from the SBA, but I recommend seeing a good attorney.
2) In order to keep your staff incentivized to stay on, it may be wise to offer them shares in your company conditional upon them saying on for e.g. 3 years. The effect of this is that your shareholding will be reduced to 80% after 3 years.
3) Sell to external investors - VC firms. Typically too small and early stage for most private equity firms who are looking for relatively large firms with sustainable cash flow from which they can lever the business with.
4) If your business is producing sustainable free cash flow, i.e. cash flow not used for expanding or expenses, and growing quickly it may make more sense not to dilute and to borrow funds from the bank, and pay yourself a dividend, but this would be the more riskier option.
Please call me or message me if you need any further clarity