The United academy player is expected to be a big player for England this summer with many supporters recognising his ability to spark his team to life.
Rashford's "flip-flap" was among those moments of excitement and earned an eighth-minute corner from which Phil Jones sent a looping header that was tipped over by Costa Rica's star man Keylor Navas.
Rashford endured a hard end to the season at United, scoring just four times in 2018 at club level, and suffering some stinging criticism from Jose Mourinho.
"We'll definitely take the things that happened in that tournament into the next one because that's going to put us in good stead".
Harry Kane and Raheem Sterling are all but assured of a place in the first match of the tournament and on this form there is every chance that Marcus Rashford will be joining them in what could be a potent trio for the Three Lions. Anything is possible and we have to go there with the highest expectations'.
"I still need to get in the box a bit more to try and finish off some chances from crossing areas, so something to learn from each game".
Rashford played in Dele Alli and his low cross found fellow substitute Welbeck at the far post.
A similar move led to the third goal as Raphael Guerreiro burst down the left and Guedes met his cross with a bullet header into the roof of the net in the 55th minute.
"Everybody's in the frame", the England coach said.
Rashford made the most of the absence of England captain Harry Kane as he started up front alongside Jamie Vardy, and showed what he is capable of with a fiercely struck shot from 25 yards that dipped perfectly into the top corner.
In other friendlies, Iceland beat Ghana 2-0 (Kari Arnason 6 and Alfreo Finnbogason 40) while South Korea and Bolivia played to a goalless draw.