[This is a response to someone wanting to become an SE, coming from a technical background with little sales experience]
A technical background is a great way to get into Sales Engineering, but you are right in that the sales side is very important as well. It isn't hard to start picking this up, and don't be afraid of your lack of experience. Many companies would highly encourage their technicians to learn better Sales skills, and there is in general a shortage of good Sales Engineers.
The biggest difference between the pre and post sales side is being able to appreciate the sales impact of what you say and what you do for prospects. Too many people start by trying to tell the customer how they should use the tool, and what problems it will solve. Customers want the product to solve their problem, so what you need to do, is listen to the customer, and think of how your company can solve their problem. You need to concentrate your response based on what they need, and treat every customer as a new response. Doing a product demo is not a "show-up-and-throw-up" solution where you give the same pitch to 100 companies and hope that it sticks to a good percentage.
My advice would be to work with your sales team, to try and sit in on webinars or sales meetings to see what happens - and not to open your mouth! One of the best skills to learn is to not say something which might hurt the deal. Sure if your product doesn't fit, you can walk away from the deal before you commit. But don't say something that will want the customer to walk away before you know if it is something you could win or not. Also, you will see how your colleagues sell the tool, and learn a bit about the product pitch. However as I said before this is not one size fits all. Also take notes of what the customer's needs are. You can then practise your demonstration skills with some target in mind about how to communicate the value of the product.
Your company might also have some small leads that the sales team doesn't have time to spend on, and you can try putting up your hand to give them a quick presentation. Every chance to communicate the value of the product is a chance for you to learn about the sales process. Also, don't be afraid to ask the sales person what the strategy is in a particular deal. You might be surprised at what value the customer sees in the product. See if you can do an internal sales pitch - if your colleagues see your abilities internally, they will be less afraid of taking you to a prospect.
Hope this is useful information for you - I started in technical support and implementation, and found that experience with end-users, project managers and business owners very useful once I got into the sales team.