Here's my basic take on it, there are 3 things to look for in a sales person
1. Product knowledge
2. Existing customer relationships
3. Understanding of the sales process and the ability to build the above 2
The trouble is
1. Most sales managers don't understand point 3
2. Point 3 I really hard to identify and quantify
So most sales managers look for one or two. No matter how good you are at 3, for most job interviews in sales they want you to prove 1 and 2.
So the best way to get into a different field of sales, practically is try to think of what else your customer base buys - for example, you sell drugs to doctors, can you leverage that to sell office management software, then leverage that to sell enterprise software? Or you sell liquor to bars, can you leverage that to sell kitchen equipment to bars, then leverage that to sell kitchen equipment to bakeries?
It's hard to jump price points, too - if you have been workin with 100 buck po's it's hard to get somebody to trust you with a 100k po but maybe you jump 100 buck to 1000 buck to 10000 to 50000.
In the end of the day, it's about getting somebody to give you a chance. I took a lot of courses and workshops when I was developing my career, and I still take a couple a year. You can learn different things.