Yes, engine braking is known to increase fuel economy marginally, but over a long trip you'll be able to notice its impact if utilised correctly. Engine braking is more efficient than normal braking and can be done by taking your foot off the accelerator and letting your engine naturally slow you down itself, you'll just need to drop down the gears as it does so.
Anticipation is key, as engine braking requires more distance to slow you down. If there's any sense of danger, you should always resort back to normal braking to ensure safety for yourself and other road users.