Picking the right ones to enter
Considering how many thousands of competitions there are, this certainly seems plausible. Most of these competitions can't have all that many entrants, which means if you're good at targeting competitions with fewer competitors, you're more likely to win.
Experienced compers recommend less desirable prizes (so no cars and holidays) and lower-profile places (so not daytime TV programmes or national newspapers). In our experience, local newspaper can potentially be a good source of prizes.
And competitions that require you to send in a postal entry or buy a product generally attract fewer entrants, as do those that require a greater element of skill, such as taking a photo, creating a video or writing a caption. Lower-value prizes also don't attract as many people.
There are websites offering automated entry to hundreds of competitions, but they will cost you and they don't necessarily improve your chances of winning. How many thousands of others enter the same competitions automatically? It's the competitions with lower accessibility that are more likely to reward the time you spend. You also run the risk of disqualification.
One way to save time is to have your address details saved in a Word or Notepad document so you can just copy and paste them into entry forms.
Time versus reward
For all the hype on the comping websites, the users seem to win relatively small, albeit with reasonable frequency if they're determined enough. The problem is compounded because, in the UK unlike in many countries, most competitions aren't obliged to display the chances of winning.
Is this right for you?
If you are going to give this a go, why not keep track of how long you spend on this over a month or two versus your winnings (and the costs you incur, if any)? If you're not winning anything, or not winning much for the time you're putting in, consider your alternatives.
You may find the odds of improving your finances will be higher if you spend all those hours working harder to get a payrise or a promotion, or developing your skills or learning new ones.