It is very true that you may be getting agents with issues. It is also true that they may be deadlisting you. There are a few things you can do to help with either of these 2 issues.
#1 Don't limit your search to just 2 companies. I'm sure the writers of the book have their own reasons, but that makes no sense. As with most businesses where people are independent contractors, it's the agent, not the company. Those may not even be the better companies for investment agents in your area. As an investment agent there are certain things I look for in choosing a broker. I need all kinds of agents working at the company because I can get my flips sold in a heartbeat by the traditional, open house, sign posting agents; I need commercial agents for my big apartment complex deals, I need land only agents when that comes up, I need REO only agents. That's the kind of diversity I'm talking about. These companies may only have 1 type and they may not want to be bothered.
#2 Ask to speak to the office manager or broker. To avoid getting the next person in line, skip the line. Explain what you are looking for and ask the managing broker to suggest someone based on what you need.
#3 Be reasonable. Make sure that the person isn't actually knee deep in an open house or on the way to a settlement when you call. They may be busy, so give the first contact a reasonable time frame. No contact in 24 hours is too long but thinking you'll have a list in 5 minutes is too much as well.
#4 Have answers to reasonable questions. When I ask someone if they will be purchasing with their own cash, hard money or traditional financing and they don't have a clue...deadlist. Even if you don't know for sure, have an answer. Script: "I will be financing my properties. I have set aside [amount of cash] and upon a recent check my credit score is about [number]. I have been researching lending options and I may be going with the [whatever loan program at whatever bank] but I am open to other options if they can refer you to someone who may have a better deal." Of course you need to actually research loan programs, the internet is your friend in this. Don't flounder; if it's one thing we agents can smell it's bad fish.
#5 Create a discussion, not one way information drain. This is your deal, do some footwork. It will benefit you in the end when you are the expert and not simply relying on the advice of someone else. Look at the market in your area, read blogs, look at prices, chart movement and on market times. The entire nationwide MLS is at your disposal if you go to www.Realtor.com. Look at it. Pinpoint an area, price range, and basic plan. If someone comes and tells me they want something East of the river, in the 2 up and coming areas noted by DC planning, that need 20-50K in work, and are currently under 300K; I can put that list together. If you come tell me to find you a deal in DC, I'm not interested in doing your job as an investor. If you ask me what I think about those 2 areas I can help you, if you ask me to analyze all neighborhoods and tell you where to invest, I'm not going to do it (steering issues).
#6 Ask how you can help yourself. If you just want "Some" listings ask the agent do they have a website with a search function. At my site my clients can visit the site, create a personal account, create their own autosearches, and mark favorites that they want me to look into. Find out if the agent has a site like this, where you can fiddle around and get all the listings you want without creating a serious tie issue for them while you're not quite ready. Sorry but my site doesn't do Arizona :).
Continue to ask around Bigger Pockets, continue to read but know it may not always apply to you, go to REI meetings and meet agents there, contact agents who are listing a lot of ugly houses. New agents are good, you can learn together, but you may also want someone who already knows, especially if you don't.
Keep at it, all the best and much success!!