Let me preface by saying, if you do your own legwork, you won't get threads full of misinformation and smarmy replies. There's a rather lengthy thread for people in your exact situation which can be found here
http://forumserver.twoplustwo.com/14...u-use-1009761/
The most convenient method to load on RPM atm is via Western Union. In that thread I linked you will find posts with detailed instructions on how to make your first WU deposit as quick and painless as possible. The fee for WU is set at $12 up to $1k. Minimum amount you can load is $100, so whether you load $100 or $1000 you're still paying the same $12.
RPM does in fact allow player to player transfers, although the Merge network is very stringent on its transfer policy. When I first joined RPM, I was told by live support (Merge) that I would have to wait three weeks from my first successful deposit to be able to transfer. I had already taken the necessary steps for player verification. The CSR told me my transfers would be automatically turned on after my 3 week "probationary" period. Whether that is true or not remains to be seen.
For UseMyWallet (UMW) you HAVE to be invited to use their service. So basically you have to go to an online casino/poker room, and have them contact UMW on your behalf. If everything's kosher, UMW will then send you an invite.
Fact: When applying for a UMW invite through RPM, you must have at least one successful deposit. Of course there's fee's like any ewallet, after all its a business.