Yes i use all my gundogs for bushing with my Lurcher, i also use them with friends Lurchers / Terriers with no problems.
Like said above they have to be finished with their training and you have to be strict with the stop whistle.( especially with Spaniels which can easily loose there heads)
I have a young Springer 8 mounth which i took on the last 2 days of the season, i will take her out bushing over the summer but will just treat it like an ordanary beating day and hunt her under control not letting her run riot with the other dogs.
My Lab on the other hand has always ran with the pack, i also let her run in and never attempt to control her in anyway with the whistle, as this would dilute any training done.
But as soon as the whistle comes out she is back to a gundog and it works very well and i tell you what you have never seen a keener hunting Lab.
And being only 21" she is Mustard in the cover.
I know 99% of Gundog trainers will be screaming "NO" at the computer screen, but if you get your training drummed into them, then do plenty of refresher training before next season, you will have some cracking fun.