well this isn't actually a trick.it's how it was meant to work.when a player signs a new contract he gets a work permit (if he doesn't have one).so if he doesn't sign the contract it doesn't mean that he snubbed it.it's just that he can't be given a work permit.there isn't an exact number of caps.it's the percent that's needed for the work permit (i think it's 75% of the nat.team's games for the last 2 years).
i've explored these options in FM2007 when i had a Polish aff.club allowing me to sign players even if they didn't get a WP.i'v found out that this method (i don't find the word "trick" appropriate in this case) works very well for players from small nations,coz when you get them to an eng club,the nat.team tends to call them,so they get the percent needed for the WP. | 
